JP2013074338A - Time server, terminal, time synchronization system, time synchronization method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To synchronize the time of a terminal to a reference time with high accuracy by discriminating a degree of congestion of a relay device without inquiring the relay device.SOLUTION: A control section 108 transmits to a terminal a reference time acquired from a clock section 107 via a transmission section 109. A packet identification section 102 receives via a receiving section 101 a first packet and a second packet having different priorities which have been transmitted by the terminal at a predetermined packet transmission interval. A receiving interval measuring section 106 measures a packet receiving interval that indicates an interval from the first packet receiving to the second packet receiving. The control section 108 creates a response packet that is a response to the second packet, and transmits the created response packet to the terminal via a transmission section 109, on the basis of a packet transmission interval contained in the first packet or the second packet, and the measured packet receiving interval.

Description

  The present invention relates to a time server, a terminal, a time synchronization system, a time synchronization method, and a program.

  In NTP (Network Time Protocol), a terminal connected to a time server via a network is based on a reference time acquired from the time server and a time required for transmission of a communication packet between the time server and the terminal. Thus, the RTC (Real Time Clock) date and time incorporated in the device is synchronized with the reference time. However, when the traffic congestion degree of the communication network (hereinafter referred to as the congestion degree) increases, a transmission delay occurs at the time of information transfer in the relay device that relays communication packets between the time server and the terminal, and is incorporated in the terminal It becomes difficult to synchronize the RTC date and time with the reference time acquired from the time server with high accuracy.

  In order to eliminate such inconvenience, a technique has been proposed in which the process of synchronizing with the reference time is performed again when the congestion degree of the communication network acquired from the relay device is equal to or greater than a predetermined threshold (see, for example, Patent Document 1). .

JP 2010-081381 A

  With the technique disclosed in Patent Document 1, when inquiries to the relay device are concentrated, the transmission delay in the relay device is further increased. For this reason, there has been a request to determine the degree of congestion of the communication network without making an inquiry to the relay device.

  The present invention has been made in view of the above circumstances, and it is possible to determine a congestion degree of a communication network without inquiring a relay device, and to synchronize the time of the terminal with a reference time with high accuracy, a time server, a terminal, and a time It is an object to provide a synchronization system, a time synchronization method, and a program.

In order to achieve the above object, a time server according to the first aspect of the present invention provides:
A timekeeping section for measuring the reference time;
A reference time acquisition unit for acquiring a reference time from the time measuring unit;
A receiving unit for receiving various packets transmitted from the terminal via the relay device;
A transmission unit that transmits other various packets to the terminal via the relay device;
Packets transmitted from the terminal at a predetermined transmission interval, received by the receiving unit that is set to have different transfer priorities in the relay device and includes the transmission interval as a packet transmission interval. A packet identification unit for identifying the first packet and the second packet,
A packet information acquisition unit for acquiring information included in the received first packet and the second packet;
Based on the reception timing of the first packet and the second packet identified by the packet identification unit, the second packet reception time that is the reception time of the second packet is acquired, and the first packet is received. A reception time information acquisition unit for acquiring a reception interval indicating an interval from when the second packet is received;
A determination unit that determines whether a difference between the packet transmission interval acquired by the packet information acquisition unit and the reception interval acquired by the reception time information acquisition unit is within a predetermined range;
A reference time packet including the reference time acquired by the reference time acquisition unit is generated, a transmission instruction is issued to the transmission unit, and the determination unit determines that the difference is within the predetermined range. A response packet that is a response packet to the second packet, and includes a response period that is a period from the second packet reception time to the transmission of the response packet, and sends a transmission instruction to the transmission unit. A packet generation unit for outputting,
It is characterized by that.

In order to achieve the above object, a terminal according to the second aspect of the present invention provides:
A timekeeping section that keeps time,
A transmission unit that transmits various packets to the time server via the relay device;
A receiving unit for receiving various other packets from the time server via the relay device;
A packet having the time server as a transmission destination, a first packet including a packet transmission interval indicating a mutual transmission interval in either one of the packets, wherein the transfer priority in the relay device is set to a different priority. A packet generation unit that generates two packets and issues an instruction to the transmission unit to transmit the first and second packets in the order of their numbers;
From the packet received by the receiving unit, if the packet is a reference time packet that includes the reference time information, the type of the packet is identified, the reference time information included in the reference time packet is acquired, and the second packet A packet information acquisition unit that acquires information on a response period that is a period from reception of the second packet at the time server to transmission of the response packet included in the response packet when the response packet is a response packet; ,
A response waiting period measurement unit that measures a response waiting period that indicates a period from when the packet generation unit issues an instruction to transmit the second packet to when the packet information acquisition unit identifies the response packet; ,
A time setting unit that sets the time of the time measuring unit based on the reference time acquired by the packet information acquisition unit, the response period, and the response waiting period measured by the response waiting period measurement unit,
It is characterized by that.

In order to achieve the above object, a time synchronization system according to the third aspect of the present invention provides:
It is comprised by the time server which concerns on the said 1st viewpoint, and the terminal which concerns on the said 2nd viewpoint.

In order to achieve the above object, a time synchronization method according to a fourth aspect of the present invention includes:
A reference time is acquired from a timekeeping unit that measures a reference time with a time server, and the acquired reference time is transmitted to the terminal via the relay device, and received at the terminal,
A first packet and a second packet, which are packets to be transmitted to the time server, wherein the priority of transfer in the relay device is set to a different priority, and one of the packets includes a packet transmission interval indicating a mutual transmission interval Generating a packet in the terminal, and
A packet transmitting / receiving step of transmitting the first packet and the second packet from the terminal and receiving the packet by the time server;
A reception interval measurement step in the time server for measuring a reception interval indicating an interval from reception of the first packet to reception of the second packet;
A determination in the time server that determines whether a difference between the packet transmission interval included in either the received first packet or the second packet and the measured reception interval is within a predetermined range Process,
A response period that is a response packet to the second packet when the difference is determined to be within a predetermined range, and is a period from when the second packet is received until preparation for transmission of the response packet is completed Generating a response packet, and instructing to transmit to the terminal via the relay device, a response packet generating step in the time server,
In response to the instruction in the response packet generating step, the generated response packet is transmitted from the time server, and the response packet is transmitted and received at the terminal.
A response waiting period measuring step in the terminal for measuring a response waiting period indicating a period from when the second packet is transmitted until the response packet is received;
Based on the reference time received from the time server, the measured response waiting period, and the response time acquired from the response packet, the time server measures the time of the time measuring unit that measures time on the terminal side A time setting step in the terminal that is set to synchronize with a reference time,
It is characterized by that.

In order to achieve the above object, a program according to the fifth aspect of the present invention provides:
On the computer,
A reference time transmission procedure for acquiring a reference time from a timer unit that measures the reference time, and transmitting the acquired reference time to the terminal via the relay device;
A packet transmitted from the terminal at a predetermined transmission interval, and a first packet including a first packet including the transmission interval as a packet transmission interval, the transfer priority of the relay device being set to different priorities A packet receiving procedure for receiving two packets via the relay device;
A reception interval measurement procedure for measuring a reception interval indicating an interval from reception of the first packet to reception of the second packet;
A determination procedure for determining whether a difference between the packet transmission interval and the reception interval is within a predetermined range;
When it is determined that the difference is within a predetermined range, a response packet that is a response packet to the second packet and includes a response period that is a period from reception of the second packet to transmission of the response packet. A response packet generation procedure to be generated;
A response packet transmission procedure for transmitting the generated response packet to the terminal via the relay device;
It is characterized by that.

In order to achieve the above object, a program according to the sixth aspect of the present invention provides:
On the computer,
A reference time receiving procedure for receiving the reference time via a relay device from a time server that transmits the reference time;
A first packet and a second packet, which are packets to be transmitted to the time server, wherein the priority of transfer in the relay device is set to a different priority, and one of the packets includes a packet transmission interval indicating a mutual transmission interval A packet generation procedure for generating
A transmission procedure for transmitting the first packet and the second packet to the time server via the relay device in the transmission interval in the order of the numbers;
A response packet that is a response packet to the second packet and that receives a response packet including a response period that is a period from when the second packet is received until the response packet is transmitted from the time server via the relay device Receiving procedure,
A response waiting period measurement procedure for measuring a response waiting period indicating a period from when the second packet is transmitted to when the response packet is received;
Based on the reference time received from the time server, the measured response waiting period, and the response time acquired from the response packet, the time of the time measuring unit that measures time is synchronized with the reference time measured by the time server. And a time setting procedure for setting to
It is characterized by that.

  ADVANTAGE OF THE INVENTION According to this invention, the congestion degree of a communication network can be discriminate | determined without inquiring a relay apparatus, and the time of a terminal can be synchronized with reference | standard time with high precision.

It is a block diagram which shows the structure of the time synchronization system which concerns on embodiment of this invention. It is a figure for demonstrating the packet transmitted / received between the time server which concerns on embodiment, a terminal, and a relay apparatus. It is a block diagram which shows the structure of the time server which concerns on embodiment. It is a figure which shows the structure of the reference | standard time packet which concerns on embodiment, a response packet, a 1st packet, and a 2nd packet. It is a figure for demonstrating the process which discriminate | determines the congestion degree of the relay apparatus based on embodiment. It is a figure for demonstrating the transmission delay of the 1st packet and 2nd packet based on Embodiment. It is a block diagram which shows the structure of the terminal which concerns on embodiment. It is a flowchart of the reference time transmission process by the timer server which concerns on embodiment. It is a flowchart of the 1st packet reception process which concerns on embodiment. It is a flowchart of the 2nd packet reception process which concerns on embodiment. It is a flowchart of the parameter acquisition process for congestion degree determination which concerns on embodiment. 6 is a flowchart of response packet generation / transmission processing according to the embodiment. It is a flowchart of the time synchronous process by the terminal which concerns on embodiment. It is a flowchart of the reference time packet reception processing according to the embodiment. It is a flowchart of the packet transmission process for congestion degree determination which concerns on embodiment. It is a flowchart of the time correction process which concerns on embodiment. It is a block diagram which shows the simplified structure of the time server which concerns on embodiment. It is a block diagram which shows the simplified structure of the terminal which concerns on embodiment.

(Embodiment)
Hereinafter, a time synchronization system 100 according to an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the time synchronization system 100 according to the present embodiment includes a time server 10 and a plurality of terminals 20 (20 ₁ , 20 ₂ ,..., 20 _n ). The time server 10 transmits a reference time to the terminal 20, and the terminal 20 sets the time of a timer unit (specifically, an RTC) that is a timer provided in the terminal 20 so as to be synchronized with the reference time. The time server 10 and the terminal 20 transmit and receive information via the relay device 30.

  Specifically, as shown in FIG. 2, the time servers 10 are different from each other, which are used to determine the degree of congestion of the relay device 30 after transmitting a reference time packet including a reference time to the terminal 20. When the first packet and the second packet transmitted from the terminal 20 with the transmission priority are received, and it is determined that the congestion degree of the relay device 30 is small based on the received first packet and second packet, the second packet As a response to, a response packet including information necessary for correcting the reference time is transmitted to the terminal 20.

  On the other hand, as shown in FIG. 2, after receiving the reference time packet from the time server 10, the terminal 20 transmits the first packet and the second packet described above to the time server 10 at a predetermined packet transmission interval. 10 receives a response packet and synchronizes the time of the terminal 20 with the reference time based on the received reference time packet and response packet. Details of the reference time packet, the first packet, the second packet, and the response packet will be described later. In FIG. 2, T0 to T6 indicate the transmission or reception time of each packet. Note that the time with parentheses is not necessarily an acquisition target.

  Hereinafter, the configuration of the time server 10 and the terminal 20 will be described, and the relay device 30 will also be described.

  The time server 10 is a device that transmits a reference time. As illustrated in FIG. 3, the time server 10 includes a reception unit 101, a packet identification unit 102, a packet buffer 103, a second packet buffer 104, and a reception time acquisition unit 105. A reception interval measuring unit 106, a time measuring unit 107, a control unit 108, and a transmitting unit 109.

  The receiving unit 101 is a part of the communication device, is configured with a communication interface or the like, and receives various information signals including packets transmitted from the terminal 20 or the like.

  The packet identification unit 102 includes a processor, a memory, a communication interface, and the like, and performs processing according to the type of received packet by executing a predetermined program stored in the memory.

  Specifically, the packet identification unit 102 identifies the type of the received packet. When the packet identification unit 102 identifies that the received packet is the first packet, the packet identification unit 102 outputs a measurement start signal instructing the reception interval measurement unit 106 to start time measurement, and stores the received packet in the packet buffer 103. To do.

  When the packet identification unit 102 determines that the received packet is the second packet, the packet identification unit 102 outputs a measurement end signal instructing the end of time measurement to the reception interval measurement unit 106, and receives the reception time acquisition unit 105. In response to this, a timing signal indicating the timing of reception time acquisition is output, and the received second packet is stored in the second packet buffer 104. Note that the packet identification unit 102 stores the received packet in the packet buffer 103 even when it is determined that the received packet is neither the first packet nor the second packet.

  The packet buffer 103 is composed of a memory or the like, and stores packets other than the second packet.

  The second packet buffer 104 includes a memory or the like, and stores the second packet identified by the packet identification unit 102.

  The reception time acquisition unit 105 is configured by, for example, a latch memory, receives a timing signal from the packet identification unit 102, and receives a timing signal from the time measuring unit 107, that is, a second time indicating the current time at which the timing signal is received, that is, the second packet is received The packet reception time is read and acquired and stored.

  The reception interval measurement unit 106 includes a timer, and in response to the measurement start signal supplied from the packet identification unit 102, clears the previous measurement results remaining in the timer to 0 and starts time measurement. In response to the measurement end signal supplied from the identification unit 102, the time measurement is ended. The timer is composed of, for example, a counter, and inputs a clock signal output from the clock signal generator of the time measuring unit 107 to the counter, starts counting the clock signal with the measurement start signal, and stops counting with the measurement end signal. Measure the elapsed time between. The measurement result is a packet reception interval (RI) indicating a time interval from the first packet reception to the second packet reception. At this time, the reception interval measurement unit 106 notifies the determination unit 1084 that the measurement of the packet reception interval (RI) is finished. When the packet identification unit 102 receives two packets before the first packet, the packet identification unit 102 does not supply a measurement start instruction signal to the packet reception interval counter.

  The timer unit 107 is a clock. The clock unit 107 includes a clock signal generator, and clocks the current date and time (reference time) based on the clock signal supplied from the clock signal generator.

  The control unit 108 includes a CPU (Central Processing Unit), a memory, and the like, and controls the overall operation of the time server 10 when the CPU executes a predetermined program stored in the memory. The control unit 108 includes a packet information acquisition unit 1081, a reference time acquisition unit 1082, a packet generation unit 1083, and a determination unit 1084 as functional components. These functions are also realized by the CPU executing a predetermined program stored in the memory.

  The packet information acquisition unit 1081 acquires information included in each of the first packet stored in the packet buffer 103 and the second packet stored in the second packet buffer 104. As will be described later, this information includes the address of the terminal that is the transmission source of the first packet and the second packet, the serial number, and the packet transmission interval (TI) included in the first packet.

  The reference time acquisition unit 1082 acquires the current time as the reference time from the time measuring unit 107 when a predetermined timing (for example, periodic or periodic date and time) comes.

  The packet generation unit 1083 generates a reference time packet from the acquired reference time, supplies the generated reference time packet to the transmission unit 109, and instructs transmission. As shown in FIG. 4A showing the configuration of various packets, the reference time packet includes a destination field for storing destination information indicating a destination address, and a source for storing source information indicating a source address. A field, a packet type field that stores packet type information indicating the type of packet, and a reference time field that stores a reference time.

  When the packet generation unit 1083 receives a notification from the determination unit 1084 described later that the degree of congestion of the relay device 30 is low, the packet generation unit 1083 responds to the terminal 20 that is the transmission source of the first and second packets with respect to the second packet. The response packet is generated, and the generated response packet is supplied to the transmission unit 109 to instruct transmission. As shown in FIG. 4B, the response packet includes a destination field, a transmission source field, a packet type field for storing information indicating the type of packet, a first packet, a second packet, and a response packet. A serial number field that stores serial number information indicating that the packet is a packet; and a response period field that stores a response period (RT) indicating a period from when the second packet is received until the response packet is transmitted. ing.

  When the determination unit 1084 receives a notification from the reception interval measurement unit 106 that the measurement of the packet reception interval (RI) is completed, the determination unit 1084 receives the packet transmission interval (TI) included in the first packet acquired by the packet information acquisition unit 1081. ) And the packet reception interval (RI) measured by the reception interval measuring unit 106, the congestion degree of the relay device 30 is determined.

  Specifically, as illustrated in FIG. 5, the determination unit 1084 includes a packet reception interval (RI) measured by the reception interval measurement unit 106 and a packet transmission interval (included in the first packet stored in the packet buffer 103). When the absolute value of the difference (D) from TI) is equal to or less than a predetermined threshold value δ (> 0) stored in the memory of the control unit 108, it is determined that the degree of congestion of the relay device 30 is small, and the difference D When the absolute value exceeds the threshold δ, it is determined that the degree of congestion of the relay device 30 is large.

  That is, the determination unit 1084 determines that the congestion degree of the relay device 30 is small when the packet transmission interval (TI) −δ ≦ packet reception interval (RI) ≦ packet transmission interval (TI) + δ is satisfied, and the packet reception interval When (RI) <packet transmission interval (TI) −δ or packet reception interval (RI)> packet transmission interval (TI) + δ is satisfied, it is determined that the degree of congestion of the relay device 30 is large.

The determination of the degree of congestion will be described in a little more detail. FIG. 6 shows an example of how the packet reception interval (RI) changes according to the packet transmission interval (TI) and the congestion degree of the relay device 30. FIG. 6A shows a case where the first packet and the second packet are transmitted from the terminal 20 to the time server 10 at the packet transmission interval (TI) with the horizontal axis as the time axis. 6B to 6E show the timing of receiving the first packet and the second packet by the time server and the packet reception interval (RI) at that time, with the horizontal axis as the time axis, and the origin of the time axis as the time axis. 6 (a) is shown in accordance with the origin of the time axis. In this example, the priority of the second packet is set higher than the priority of the first packet. For example, the priority of the first packet is set to the normal priority, and the priority of the second packet is set to the highest priority. FIG. 6B shows that the congestion degree of the relay device 30 is small. When the transmission delay period of the first packet at this time is α ₁ and the transmission delay period of the second packet is β ₁ , α ₁ and β ₁ are almost the same. Indicates the same. The packet reception interval (RI) at this time is equal to the packet transmission interval (TI). Therefore, the difference D between the two is almost 0, and the absolute value thereof is not more than the predetermined threshold value δ. That is, FIG. 6B is a case where it is determined that the degree of congestion is small because the absolute value of the difference D is less than or equal to the threshold δ.

FIG. 6C shows a case where the degree of congestion of the relay device 30 is larger than that in the case of FIG. When the transmission delay time of the first packet at that time and α _2, α ₂ is greater than alpha ₁ by an increase in congestion. On the other hand, the transmission delay period of the second packet remains β ₁ because the priority is set high. Therefore, the packet reception interval (RI) is smaller than the packet transmission interval (TI), and the absolute value of the difference D increases compared to the case of FIG. As the degree of congestion increases, the transmission delay period of the first packet becomes larger than the transmission delay period of the second packet, and the packet reception interval (RI) becomes smaller. Therefore, the absolute value of the difference D increases as the degree of congestion increases. When the criterion for determining the response packet transmission is a case where the degree of congestion is equal to or lower than a predetermined level (this is called a case where the degree of congestion is low), the predetermined level is replaced with a level relative to the absolute value of the difference D, and the threshold δ When the absolute value of the difference D is less than or equal to the threshold δ, it is determined that the degree of congestion is small.

FIG. 6 (d) shows a case where the degree of congestion is greater than that in FIG. 6 (c). At this time, the transmission delay period of the second packet remains β ₁ because the priority is set high, but the transmission delay period of the first packet becomes α ₃ which is larger than α ₂ , The packet is received later than the second packet. In such a case, the determination based on the absolute value of the difference D is meaningless. Therefore, it is determined that the degree of congestion is high with the reverse of the reception order, and the response packet is not transmitted.

  In the example shown in FIGS. 6B to 6D, the transmission delay period of the second packet is not changed depending on the degree of congestion. However, when a packet with a high priority competes, the transmission delay period shown in FIG. As shown, the transmission delay period of the second packet may be longer than in the case of FIGS. However, even in such a case, since the transmission delay period of the second packet is smaller than the transmission delay period of the first packet, the packet reception interval (RI) is usually smaller than the packet transmission interval (TI). Thus, the explanation so far is valid as it is.

  If the determination unit 1084 determines that the degree of congestion of the relay device 30 is small, the determination unit 1084 notifies the packet generation unit 1083 to that effect. If the determination unit 1084 determines that the degree of congestion of the relay device 30 is large, the determination unit 1084 does not notify the packet generation unit 1083 of the fact.

  The transmission unit 109 is a part of the communication device and is configured by a communication interface or the like, and transmits various information signals including packets to the terminal 20. For example, a packet supplied from the packet generation unit 1083 and instructed to transmit is transmitted to the terminal 20 or the like.

  The terminal 20 is a computer that synchronizes with a reference time. As illustrated in FIG. 7, the terminal 20 includes a transmission unit 201, a reception unit 202, an operation unit 203, a display unit 204, a storage unit 205, and a control unit 206. And a time measuring unit 207.

  The transmission unit 201 and the reception unit 202 are configured by a communication interface or the like as a communication unit, and transmit and receive various signals including packets to and from the time server 10 and the like via the relay device 30.

  The operation unit 203 includes a keyboard, a mouse, and the like, and supplies an operation signal corresponding to a user operation to the control unit 206.

  The display unit 204 includes an LCD (Liquid Crystal Display) or the like, and displays various images under the control of the control unit 206.

  The storage unit 205 includes a memory or the like, and stores various types of information that will be described later.

  The control unit 206 includes a CPU, a memory, and the like, and controls the overall operation of the terminal 20 when the CPU executes a predetermined program stored in the memory. The control unit 206 includes a packet information acquisition unit 2061, a packet generation unit 2062, a response waiting period acquisition unit 2063, a time setting unit 2064, and a time correction unit 2065 as functional components. Each of these functions described later is also realized by the CPU executing a predetermined program stored in the memory.

  The packet information acquisition unit 2061 acquires information included in the packet received via the reception unit 202. This information is the source address, packet type, and reference time if the received packet is a reference time packet. If the received packet is a response packet, this information is the source address, packet type, and serial number. And a response period (RT). When the packet information acquisition unit 2061 determines from the information in the packet type field that the received packet is a reference time packet, the packet information acquisition unit 2061 notifies the time setting unit 2064 of the reference time acquired from the packet.

  When the packet information acquisition unit 2061 determines from the information in the packet type field that the received packet is a response packet, the packet information acquisition unit 2061 acquires the current time as the reception time of the response packet from the time measuring unit 207 and stores it. The information is stored in the unit 205 and the response waiting period acquisition unit 2063 is notified that the response packet has been received.

  The packet generation unit 2062 generates a first packet and a second packet that are used to determine the degree of congestion of the relay device 30, and transfers the generated first packet to the transmission unit 201 at the relay device 30. Is set to a predetermined priority A, and an instruction to transmit to the time server 10 is issued, and after the transmission instruction of the first packet, the packet transmission interval (TI) stored in the storage unit 205 is set. When the time elapses, the second packet is set to have a priority related to transfer in the relay device 30 at a priority different from the priority A, for example, a priority B that is higher than the priority A. To instruct the time server 10 to transmit. In addition, in the transmission instruction, the packet generation unit 2062 acquires the current date and time when issuing the second packet transmission instruction from the time measuring unit 207, and stores the acquired date and time in the storage unit 205 as the second packet transmission time. .

  As shown in FIG. 4C, the first packet includes a destination field, a transmission source field, a packet type field, and a priority field for storing priority information when the relay device 30 relays the packet. , A serial number field, and a packet transmission interval field for storing a packet transmission interval (TI).

  On the other hand, as shown in FIG. 4D, the second packet includes a destination field, a transmission source field, a packet type field, a priority field, and a serial number field.

  When receiving a response packet reception notification from the packet information acquisition unit 2061, the response waiting period acquisition unit 2063 reads the response packet reception time and the second packet transmission time from the storage unit 205, and calculates the difference between them as a response waiting period (RWT ) And notify the time correction unit 2065.

  When receiving the notification of the reference time from the packet information acquisition unit 2061, the time setting unit 2064 sets the reference time in the time measuring unit 107. Further, when receiving a response waiting period (RWT) notification from the response waiting period acquisition unit 2063, the time setting unit 2064 performs time correction processing, and corrects the current time of the time measuring unit 207 based on the result. Specifically, the time setting unit 2064 calculates a transmission delay period (DT) indicating a period required for packet transmission between the time server 10 and the terminal 20 based on the following relational expression. Transmission delay period (DT) = (response waiting period (RWT) −response period (RT) included in response packet) / 2. The time setting unit 2064 corrects the current date and time counted by the time measuring unit 207 so as to advance by the calculated transmission delay period (DT).

  The timekeeping unit 207 is a clock, and is composed of, for example, an RTC.

  The relay device 30 shown in FIG. 1 is configured by a switching hub or the like, relays a packet transmitted from the time server 10 to a terminal 20 or the like corresponding to a destination included in the packet, and converts the packet transmitted from the terminal 20 into a packet. Relay to the time server 10 corresponding to the destination included. When the packet includes a priority for transferring the packet, the relay device 30 relays the packet based on the priority.

  The priority at which the relay apparatus 30 transfers a packet is specified by PCP (Priority Code Point) defined by IEEE802.1p, DSCP (DiffServ Code Point) defined by RFC2474, or the like. The priority designation method is arbitrary, but the priority designated by the first packet and the second packet is the priority at the relay device 30.

  Next, operations of the time server 10 and the terminal 20 constituting the time synchronization system 100 will be described.

  The time server 10 transmits the reference time to the terminal 20 as a general time server, and is transmitted with different priorities set from the terminal 20 used to determine the degree of congestion of the relay device 30. When the packet and the second packet are received via the relay device 30, and it is determined that the congestion degree of the relay device 30 is small based on the received first packet and second packet, a response packet is generated, and the terminal 20 It performs the characteristic operation of transmitting to.

  On the other hand, in addition to operating as a general computer, the terminal 20 receives a reference time packet from the time server 10 and then transmits a first packet and a second packet having different priorities to a predetermined packet transmission interval (TI). When the time server 10 transmits a response packet to the time server 10 via the relay device 30, the terminal 20 receives the response packet and based on the received reference time packet and the response packet. A characteristic operation is performed in which the time is corrected and synchronized with the reference time measured by the time server 10.

  Hereinafter, in order to facilitate understanding, the characteristic operation of the time server 10 and the terminal 20 will be mainly described with reference to an example in which one terminal 20 receives a reference time from the time server 10 and synchronizes the time. .

  The control unit 108 of the time server 10 starts the reference time transmission process shown in FIG. 8 when a predetermined timing (for example, periodic or periodic date and time) is reached. Transition between the steps shown in FIG. 8 is controlled by the control unit 108.

  In this process, first, the packet generator 1083 generates a reference time packet shown in FIG. 4A (step S1). The reference time included in the reference time packet is acquired from the time measuring unit 107 by the reference time acquisition unit 1082.

  Specifically, the packet generation unit 1083 sets the IP address of the terminal 20 stored in advance in the memory of the control unit 108 in the destination field of the reference time packet, and the packet generation unit 1083 stores the IP address stored in advance in the memory of the control unit 108. Is set in the transmission source field of the reference time packet. Further, the packet generation unit 1083 sets the packet type information indicating the “reference time packet” in the packet type field. Further, the packet generator 1083 acquires the reference time that is the current time at that time from the timer 107, and sets the acquired reference time in the reference time field of the reference time packet. In this way, the packet generator 1083 generates a reference time packet.

  The packet generator 1083 transmits the generated reference time packet via the transmitter 109 (step S2).

  Next, the time server 10 starts reception processing of the first packet and the second packet transmitted from the terminal 20 that has received the reference time packet to determine the congestion degree of the relay device 30.

  The receiving unit 101 of the time server 10 determines whether or not a packet has been received (step S3). If no packet is received (step S3; NO), it is determined whether or not a predetermined time has passed (step S6). If the predetermined time has not passed (step S6; NO), the process returns to step S3 to receive the packet. wait. If the predetermined time has elapsed (step S6; YES), the process returns to step S1, and the reference time packet is generated and transmitted again. This is because when a very long time has elapsed after transmitting the reference time packet, it is determined when the reference time packet is transmitted and when the congestion degree of the relay device 30 is determined (that is, when the first packet and the second packet are received). This is because the degree of congestion of the relay device 30 changes, so that the reference time packet is transmitted again.

  If a packet is received (step S3; YES), the packet identification unit 102 identifies the type of packet and determines whether the received packet is the first packet (step S4). When the packet identification unit 102 determines that the received packet is the first packet (step S4; YES), a first packet reception process is executed (step S5). When the first packet reception process ends, the process returns to step S3 and waits for reception of the next packet.

  In step S3, it is determined again whether or not a packet has been received. If a packet is received (step S3; YES), the packet identification unit 102 identifies the type of the packet and determines whether or not the received packet is the first packet. (Step S4). Here, since the first packet has already been received, the received packet is not the first packet (step S4; NO). Therefore, the packet identification unit 102 determines whether or not the received packet is the second packet (step S7). If it is determined that the packet is not the second packet (step S7; NO), the process proceeds to step S6, and the processing described above is executed.

  When determining that the received packet is the second packet (step S7; YES), the packet identification unit 102 determines whether the first packet having the same serial number has already been received (step S8). If the first packet has not been received (step S8; NO), the process returns to step S1. This is because when the reception order of the first packet and the second packet is different from the transmission order, it is difficult to evaluate the congestion level, and the reference time packet is retransmitted. Note that the case where the order is reversed in this way corresponds to a case where the degree of congestion is large as will be described later, and it can be said that returning to the retransmission of the reference time packet is a reasonable process.

  When the first packet is received (step S8; YES), the control unit 108 executes the second packet reception process (step S9), and executes the congestion degree determination parameter acquisition process in response to the result. (Step S10). The determination unit 1084 of the control unit 108 determines the congestion level of the relay device 30 in response to the result of the congestion level determination parameter acquisition process (step S11).

  When the determination unit 1084 determines that the degree of congestion is large (step S11; NO), the control unit 108 returns the process to step S1. In such a case, it can be determined that the congestion level is large even when the reference time packet is transmitted, and the transmission delay of the reference time packet transmitted at a time when the congestion level is large is likely to fluctuate greatly. As a difficulty, the reference time packet is retransmitted.

  When the determination unit 1084 determines that the degree of congestion is small (step S11; YES), the control unit 108 executes response packet generation / transmission processing (step S12), and sends a response packet to the terminal 20 via the relay device 30. Send.

  In FIG. 8, when the packet identification unit 102 determines that the received packet is neither the first packet nor the second packet (step S7 in FIG. 8; NO), the received packet is transmitted as a reference time. Since it is not an object of processing, it is excluded from FIG. 8 and is processed separately.

  Next, the first packet reception process (step S5), the second packet reception process (step S9), the congestion degree determination parameter acquisition process (step S10), the congestion degree determination process (step S11), and the response shown in FIG. Details of the packet generation / transmission process (step S12) will be described.

  FIG. 9 shows a flowchart of the first packet reception process. When the packet identification unit 102 determines that the received packet is the first packet based on the packet type information set in the packet type field of the received packet (step S4 in FIG. 8; YES), measurement starts The signal is output to the reception interval measurement unit 106 (step S20). Further, the packet identification unit 102 stores the received first packet in the packet buffer 103 (step S21), and the control unit 108 ends the first packet reception process, returns to step S5 in FIG. The process proceeds to step S3.

  The reception interval measurement unit 106 starts measuring the packet reception interval (RI) in response to the measurement start signal supplied from the packet identification unit 102.

  FIG. 10 shows a flowchart of the second packet reception process. Based on the packet type information set in the packet type field of the received packet, the packet identification unit 102 determines that the received packet is the second packet and determines that the first packet has been received. In the case (step S7 in FIG. 8; YES, step S8; YES), a measurement end signal is output to the reception interval measurement unit 106 (step S30). At the same time, the packet identification unit 102 outputs a timing signal to the reception time acquisition unit 105. In response to the timing signal, the reception time acquisition unit 105 acquires and holds the current date and time (T4) as the second packet reception time (T4) from the time measuring unit 107 (step S31). Further, the received second packet is stored in the second packet buffer 104 (step S32), and the control unit 108 ends the second packet reception process, returns to S9 in FIG. 8, and proceeds to the next step S10. To do.

  In response to the measurement end signal supplied from the packet identification unit 102, the reception interval measurement unit 106 ends the measurement of the packet reception interval (RI), holds the measurement result, and determines that the measurement has ended. 1084 is notified.

  FIG. 11 is a flowchart of the congestion degree determination parameter acquisition process. The congestion degree determination parameter is a difference (D) between a packet reception interval (RI) and a packet transmission interval (TI) used for determination of the congestion degree.

  Upon receiving a notification that the measurement of the packet reception interval (RI) has ended, the determination unit 1084 acquires the packet reception interval (RI) from the reception interval measurement unit 106 (step S40). Further, the determination unit 1084 acquires the packet transmission interval (TI) via the packet information acquisition unit 1081 (step S41). The determination unit 1084 calculates a difference (D) between the acquired packet reception interval (RI) and the acquired packet transmission interval (TI) (step S42), and the control unit 108 ends the congestion degree determination parameter acquisition processing. Then, the process returns to step S10 in FIG. 8, and the process proceeds to step S11.

  In step S11 of FIG. 8, the determination unit 1084 determines whether the degree of congestion is small. Specifically, the absolute value of the difference (D) is equal to or less than a predetermined threshold value δ stored in the memory of the determination unit 1084. It is discriminate | determined whether it is (step S11). When the determination unit 1084 determines that the absolute value of the difference D exceeds the threshold δ, that is, when the determination unit 1084 determines that the degree of congestion is large (step S11; NO), as described above, the control unit 108 performs the process in step S1. Return to.

  On the other hand, when the determination unit 1084 determines that the absolute value of the difference D is equal to or less than the threshold δ (step S11; YES), the packet generation unit 1083 is notified that the degree of congestion of the relay device 30 is small, as already described. The control unit 108 executes response packet generation / transmission processing (step S12).

  FIG. 12 shows a flowchart of response packet generation / transmission processing. When the packet generation unit 1083 receives a notification from the determination unit 1084 that the degree of congestion of the relay device 30 is small, the packet generation unit 1083 starts the response packet generation / transmission process illustrated in FIG.

  In preparation for generating a response packet, the packet generation unit 1083 acquires the current date and time (T5) as the response packet transmission time (T5) from the time measuring unit 107, and transmits the response packet transmission time (T5) and the reception time acquisition unit 105. By calculating the difference from the second packet reception time (T4) acquired in step 4, a response period (RT) indicating a period from when the second packet is received until the response packet is transmitted is calculated (step S50). Then, the response packet shown in FIG. 4B is generated (step S51).

  Specifically, the packet generation unit 1083 sets the transmission source information included in the second packet acquired through the packet information acquisition unit 1081 in the destination field of the response packet, and sets the destination information included in the second packet. Set in the source field of the response packet. Subsequently, the packet generation unit 1083 sets the packet type information indicating “response packet” in the packet type field of the response packet. Further, the packet generation unit 1083 sets the serial number information included in the second packet in the serial number field of the response packet, and sets the calculated response period (RT) in the response period field of the response packet. In this way, the packet generator 1083 generates a response packet.

  The packet generation unit 1083 transmits the generated response packet via the transmission unit 109 (step S52). Thereafter, the process returns to step S12 in FIG. 8, and the control unit 108 ends the reference time transmission process.

  Next, time synchronization processing at the terminal 20 that has transmitted the reference time packet from the time server 10 will be described. FIG. 13 shows a flowchart of the time synchronization process.

  The control unit 206 of the terminal 20 starts packet reception processing, determines whether or not a packet is received via the reception unit 202 (step S60), and if no packet is received (step S60; NO), returns to step S60. Wait for reception. If there is a packet received (step S60; YES), the packet information acquisition unit 2061 of the control unit 206 receives the packet based on the packet type information set in the packet type field of the packet received via the reception unit 202. It is determined whether or not the received packet is a reference time packet (step S60).

  If the received packet is a reference time packet (step S61; YES), the control unit 206 executes a reference time packet reception process (step S62), and then executes a congestion degree determination packet transmission process (step S63). . Thereafter, the process returns to step S60.

  If the received packet is not a reference time packet (step S61; NO), the packet information acquisition unit 2061 determines whether or not the received packet is a response packet (step S64), and is not a response packet (step S64). NO), the control unit 206 returns the process to step S60.

  In FIG. 13, when the packet information acquisition unit 2061 determines that the received packet is neither a reference time packet nor a response packet (step S64; NO in FIG. 13), Since it is not a target of the synchronization process, it is excluded from FIG. 13 and is processed separately.

  If the received packet is a response packet (step S64; YES), the control unit 206 executes time correction processing (step S65) and ends the time synchronization processing.

  Next, the reference time packet reception process (step S62), the congestion degree determination packet transmission process (step S63), and the time correction process (step S65) will be described in detail.

  FIG. 14 shows a flowchart of the reference time packet reception process. The packet information acquisition unit 2061 stores the received reference time packet information in the storage unit 205 (step S70). Subsequently, the time setting unit 2064 sets the current date and time of the time measuring unit 207 so as to coincide with the stored reference time (step S71), ends the reference time packet reception process, and the control unit 206 performs the process. Is advanced to the congestion degree determination packet transmission process (step S63) of FIG.

  Since the transmission delay of the reference time packet is not considered in the time setting at this time, the current date and time of the time measuring unit 207 after the setting is compared with the reference time measured by the time measuring unit 107 of the time server 10. Delayed by the packet transmission delay.

  FIG. 15 is a flowchart of the congestion degree determination packet transmission process. The control unit 206 starts the congestion degree determination packet transmission process shown in FIG. 15 by a call from the packet reception process, and first generates the first packet shown in FIG. 4C (step S80).

  Specifically, the packet generation unit 2062 sets the transmission source information included in the reference time packet stored in the storage unit 205 in the destination field of the first packet, and sets the destination information included in the reference time packet to the first packet. Set in the source field of. By setting in this way, the destination of the first packet is set to the time server 10 that has transmitted the reference time packet, and the transmission source of the first packet is set to the terminal 20 that has received the reference time packet.

  Subsequently, the packet generation unit 2062 sets the packet type information indicating “first packet” in the packet type field of the first packet. Further, the packet generation unit 2062 has priority information (for example, priority) indicating that the relay apparatus 30 sets the priority for transferring the first packet to a lower priority than the second packet, for example, the same priority as that of a normal packet. Is set in the priority field of the first packet.

  The packet generation unit 2062 sets an arbitrary integer N in the serial number field of the first packet. The packet generation unit 2062 increments (+1) the integer N every time the first packet is generated. Subsequently, the packet generation unit 2062 sets the packet transmission interval (TI) stored in the storage unit 205 in the packet transmission interval field of the first packet. In this way, the packet generation unit 2062 generates the first packet.

  Next, the packet generator 2062 generates the second packet shown in FIG. 4D (step S81). Specifically, the packet generation unit 2062 sets destination information and transmission source information in the destination field and transmission source field of the second packet, respectively, in the same manner as the first packet. Subsequently, the packet generation unit 2062 sets the packet type information indicating “second packet” in the packet type field of the second packet. Further, the packet generation unit 2062 sets priority information indicating that the priority of the relay device 30 to transfer the second packet is higher than the priority of the first packet in the priority field of the second packet.

  The packet generator 2062 sets the integer N set in the first packet in the serial number field of the second packet. The first packet and the second packet having the same setting value in the sequence number field constitute a set of packets. In this way, the packet generator 2062 generates the second packet.

  The packet generation unit 2062 transmits the generated first packet to the time server 10 via the transmission unit 201 (step S82), and determines whether the packet transmission interval (TI) has elapsed since the transmission (step S82). S83). If it has not elapsed (step S83; NO), the process returns to step S83, repeats step S83, and waits until it elapses.

  When the packet transmission interval (TI) has elapsed (step S83; YES), the packet generation unit 2062 transmits the generated second packet to the time server 10 via the transmission unit 201 (step S84).

  The packet generation unit 2062 acquires the time T3 when the transmission instruction of the second packet is issued to the transmission unit 201 from the time measuring unit 207, and stores the acquired time (T3) as the second packet transmission time (T3). The data is stored in 205 (step S85). Then, the control unit 206 ends the congestion degree determination packet transmission process, and returns the process from step S63 to step S60 in FIG.

  FIG. 16 shows a flowchart of time correction processing. When it is determined in step S64 in FIG. 13 that a response packet has been received (step S64 in FIG. 13; YES), the control unit 206 calls and executes a time correction process.

  When it is determined that the response packet has been received, the packet information acquisition unit 2061 acquires the current date and time (T6) as the response packet reception time (T6) from the time measuring unit 207 (step S90). Further, the packet information acquisition unit 2061 acquires information including the response period of the received response packet (step S91).

  Next, the response waiting period acquisition unit 2063 calculates the response waiting period (RWT) by taking the difference between the acquired response packet reception time (T6) and the second packet transmission time (T3) (step S92). .

  Subsequently, the time setting unit 2064 calculates a transmission delay period (DT) based on, for example, the following relational expression (step S93). Transmission delay period (DT) = (calculated response waiting period (RWT) −response period (RT) included in response packet) / 2. The time setting unit 2064 corrects the current date and time measured by the time measuring unit 207 so as to advance by the calculated transmission delay period (DT) (step S94), ends the time correction process, and the control unit 206 performs the process shown in FIG. The time synchronization process shown is terminated.

  As described above, after transmitting the reference time packet including the reference time to the terminal 20, the time server 10 uses the first packet and the first packet having different transmission priorities used to determine the congestion degree of the relay device 30. Two packets are received from the terminal 20, and when it is determined that the degree of congestion of the relay device 30 is small based on the received first packet and second packet, a response packet is transmitted to the terminal 20. For this reason, the time server 10 can determine the congestion degree of the relay device without inquiring of the relay device 30. Since the time server 10 transmits the response packet when the degree of congestion of the relay device 30 is small, the transmission delay when the response packet is transmitted is small. Therefore, the reference transmitted at a time close to the time when the response packet is transmitted. It can be expected that the transmission delay of the time packet is also small. Therefore, the terminal 20 can synchronize the time with the reference time with high accuracy by performing time setting and correction according to the response packet.

  The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the invention. For example, the configuration and operation of the hardware shown in the above description are merely examples, and the present invention is not limited thereto, and can be appropriately changed and applied within the scope of the invention as illustrated below.

  In the above embodiment, the control unit 206 includes the packet transmission interval (TI) in the first packet, but may include the packet transmission interval (TI) in the second packet. If the time server 10 can acquire the information of the packet transmission interval (TI) when the time server 10 receives the second packet, the subsequent processing can be performed in the same manner. In this case, the same effect as that of the above-described invention can be obtained. be able to.

  In the above embodiment, the packet transmission interval (TI) is a fixed value, but the control unit 206 includes a transmission interval adjustment unit, and when the transmission interval adjustment unit can receive a response packet, the next reference time The packet transmission interval (TI) during transmission of the first packet and the second packet accompanying transmission is reduced by a predetermined time, and when a response packet cannot be received, the packet transmission interval (TI) is increased by a predetermined time. You may do it.

  Until now, it is assumed that the degree of congestion of the relay device 30 from the reference time packet transmission to the completion of the first and second packet transmissions does not change. However, if the packet transmission interval (TI) is large, the degree of congestion may change during that time, so the packet transmission interval (TI) is preferably as small as possible. On the other hand, if the packet transmission interval (TI) is decreased, the reception order of the first packet and the second packet at the terminal 20 is reversed even when the congestion degree is not so large, and the response packet cannot be received. There is a fear. Therefore, the packet transmission interval (TI) is adjusted according to the response packet reception status. This measure makes it possible to reduce the packet transmission interval (TI) in a situation where the degree of congestion can be evaluated, and to improve the reliability of time synchronization.

  Moreover, in the said embodiment, although the priority at the time of transferring the 1st packet in the relay apparatus 30 is set lower than the priority at the time of transferring the 2nd packet, it is not limited to this, For example, The priority for transferring the first packet may be set higher than the priority for transferring the second packet. In this case, the difference D has the opposite sign as in the above embodiment, but the congestion value of the relay device 30 is determined by comparing the absolute value of the difference D with a predetermined threshold, so that the congestion is the same as before. The degree can be determined. Therefore, also in this case, the same effect as that of the above invention can be obtained.

  Further, when the priority is set in this way, when the congestion level becomes high, the packet reception interval (RI) is increased, and the reception timing of the first packet and the second packet is not reversed. Therefore, it is possible to avoid a situation in which the response packet due to such reverse rotation is not transmitted, and therefore it is possible to reduce the packet transmission interval (TI) as much as possible.

  As described above, the reception interval measuring unit 106 includes a counter and a clock signal generator, and counts up the packet reception interval by up-counting in response to the measurement start signal and stopping the count in response to the measurement end signal. However, the present invention is not limited to this, and packet transmission interval (TI) + δ + 1 is preset as a count value, down-counts in response to a measurement start signal, and down-count is stopped by a measurement end signal. Also good. In this case, the determination unit 1084 may determine that the traffic congestion degree of the relay device 30 is small when the count value of the counter is “1” or more and “2 × δ + 1” or less. When the count value becomes 0 in the middle, the count is automatically stopped. When the count is automatically stopped, since the count value is 0, it is determined that the degree of congestion of the relay device 30 is large.

  Note that the reception interval measuring unit 106 is not limited to a counter. The reception interval measuring unit 106 may be configured to measure the reception times of the first packet and the second packet and use the difference as the packet reception interval. Specifically, the packet identification unit 102 outputs timing signals for the first packet and the second packet to the reception interval measurement unit 106 at the timing of receiving the first packet and the timing of receiving the second packet. This timing signal corresponds to the previous measurement start signal and measurement end signal. The reception interval measuring unit 106 obtains the current time from the time measuring unit 107 at the time of each timing signal input, and uses the difference as the packet reception interval (RI) as the first packet reception time and the second packet reception time. When the first packet reception time is later than the second packet reception time, the difference is a negative number, so that no response packet is generated. Even when the reception interval measuring unit 106 is configured as described above, the same effects as those described above can be obtained.

  The reception interval measurement unit 106 in the case of including the above-described modification receives the first packet after receiving the first packet based on the reception timings of the first packet and the second packet identified by the packet identification unit 102. It is possible to obtain the reception interval of both packets indicating the interval until reception of.

  Although the determination unit 1084 is included in the control unit 108, the determination unit 1084 may be configured independent of the control unit 108.

  FIG. 17 shows a simplified configuration according to the time server 10 of the present embodiment. The same numbers as those shown in FIG. 3 have the same functions. The component not described in FIG. 3 is the reception time information acquisition unit 111, and the number of the packet information acquisition unit 110 is also different from that in FIG. Further, in FIG. 3, an arrow is added where there is no arrow. Among these, the packet information acquisition unit 110 corresponds to the packet information acquisition unit 1081 of FIG. 3 with the packet buffer 103 and the second packet buffer 104 added. However, the packet buffer 103 and the second packet buffer 104 may not be included as long as it has a function of acquiring packet information. Accordingly, the function is the same as that of the packet information acquisition unit 1081 in FIG. 3, so the name is shared but the number is changed. The reception time information acquisition unit 111 has a function that combines the functions of the reception time acquisition unit 105 and the reception interval measurement unit 106 of FIG. The function of the reception interval measurement unit 106 is not limited to that configured with a counter, and may be the above-described modification. Since the reception time acquisition unit 105 and the reception interval measurement unit 106 can be configured to include a common function depending on the specific embodiment, both functions are combined. The arrows are attached according to the contents of the description of the operation, and the operation of the time server 10 shown in FIG. 17 is as described in the flowchart so far.

  FIG. 18 shows a simplified configuration according to the terminal 20 of the present embodiment. The same numbers as those shown in FIG. 7 have the same functions. Although there are no components not shown in FIG. 7, in FIG. 7, the parts not indicated by arrows are also provided with arrows. The arrows are attached according to the contents of the description of the operation, and the operation of the terminal 20 shown in FIG. 18 is as described in the flowchart so far.

  In the description so far, there is first the generation of the reference time packet in the time server 10 and the transmission to the terminal 20, and then the first packet and the second packet are transmitted from the terminal 20 to the time server 10. It is not necessary to be limited to this order. The reference time packet may be transmitted when the response packet is transmitted. At this time, either the reference time packet or the response packet may be transmitted first. Furthermore, the transmission of the reference time packet may be omitted, and the response packet may be transmitted including the reference time. In this case, first, the time server 10 transmits a preparation signal indicating that the reference time is to be transmitted to the terminal 20, and after receiving the preparation signal, the terminal 20 transmits the first packet and the second packet as described above. To the time server 10. After receiving the first packet and the second packet, the time server 10 evaluates the degree of congestion of the relay device 30 in the same manner as described above, and generates a response packet when it is determined that the degree of congestion is low. Send to. In the modified example described here, the packet generation unit 1083 of the time server 10 generates a response packet including the reference period together with the response period (RT). The terminal 20 sets the reference time in the time measuring unit 207 of the terminal and executes time correction processing as described above.

  In either case, the time server 10 transmits the reference time to the terminal 20 only when the response packet is transmitted, that is, when the congestion degree of the relay device 30 is small, so that the time of the terminal 20 is timed with higher accuracy. This is synchronized with the reference time of the server 10.

  Further, the terminal 20 may be a PDA (Personal Digital Assistants), a mobile phone, a game machine or the like in addition to the computer exemplified in the above embodiment.

  In addition, the time synchronization system 100 according to the present embodiment can be realized using a normal computer system, not a dedicated system. For example, by storing a program for executing the above-described operation in a computer-readable recording medium (flexible disk, CD-ROM, DVD-ROM, etc.) and installing the program in the computer, You may comprise the time synchronization system 100 which performs the above-mentioned process. Alternatively, the time synchronization system 100 may be configured by storing the program in a storage device included in a file identification device on a communication network such as the Internet and downloading the program by a normal computer system.

  When the functions of the time synchronization system 100 are realized by sharing of an OS (operating system) and an application program, or by cooperation between the OS and the application program, only the application program portion is stored in a recording medium or a storage device. May be.

  It is also possible to superimpose a program on a carrier wave and distribute it via a communication network. For example, this program may be posted on a bulletin board (BBS: Bulletin Board System) on a communication network, and the program may be distributed via the network. The program may be started and executed in the same manner as other application programs under the control of the OS, so that the above-described processing can be executed.

  A part or all of the above-described embodiment can be described as in the following supplementary notes, but is not limited thereto.

(Appendix 1)
A timekeeping section for measuring the reference time;
A reference time acquisition unit for acquiring a reference time from the time measuring unit;
A receiving unit for receiving various packets transmitted from the terminal via the relay device;
A transmission unit that transmits other various packets to the terminal via the relay device;
Packets transmitted from the terminal at a predetermined transmission interval, received by the receiving unit that is set to have different transfer priorities in the relay device and includes the transmission interval as a packet transmission interval. A packet identification unit for identifying the first packet and the second packet,
A packet information acquisition unit for acquiring information included in the received first packet and the second packet;
Based on the reception timing of the first packet and the second packet identified by the packet identification unit, the second packet reception time that is the reception time of the second packet is acquired, and the first packet is received. A reception time information acquisition unit for acquiring a reception interval indicating an interval from when the second packet is received;
A determination unit that determines whether a difference between the packet transmission interval acquired by the packet information acquisition unit and the reception interval acquired by the reception time information acquisition unit is within a predetermined range;
A reference time packet including the reference time acquired by the reference time acquisition unit is generated, a transmission instruction is issued to the transmission unit, and the determination unit determines that the difference is within the predetermined range. A response packet that is a response packet to the second packet, and includes a response period that is a period from the second packet reception time to the transmission of the response packet, and sends a transmission instruction to the transmission unit. A packet generation unit for outputting,
A time server characterized by this.

(Appendix 2)
The packet generation unit generates the reference time packet when the determination unit determines that the difference is within the predetermined range, and issues a transmission instruction to the terminal to the transmission unit.
The time server according to appendix 1, wherein

(Appendix 3)
The packet generation unit replaces the generation of the reference time packet by generating the response packet including the reference time.
The time server according to Supplementary Note 2, wherein

(Appendix 4)
A timekeeping section that keeps time,
A transmission unit that transmits various packets to the time server via the relay device;
A receiving unit for receiving various other packets from the time server via the relay device;
A packet having the time server as a transmission destination, a first packet including a packet transmission interval indicating a mutual transmission interval in either one of the packets, wherein the transfer priority in the relay device is set to a different priority. A packet generation unit that generates two packets and issues an instruction to the transmission unit to transmit the first and second packets in the order of their numbers;
From the packet received by the receiving unit, if the packet is a reference time packet that includes the reference time information, the type of the packet is identified, the reference time information included in the reference time packet is acquired, and the second packet A packet information acquisition unit that acquires information on a response period that is a period from reception of the second packet at the time server to transmission of the response packet included in the response packet when the response packet is a response packet; ,
A response waiting period measurement unit that measures a response waiting period that indicates a period from when the packet generation unit issues an instruction to transmit the second packet to when the packet information acquisition unit identifies the response packet; ,
A time setting unit that sets the time of the time measuring unit based on the reference time acquired by the packet information acquisition unit, the response period, and the response waiting period measured by the response waiting period measurement unit,
A terminal characterized by that.

(Appendix 5)
A transmission interval adjustment unit that adjusts the transmission interval according to whether the reception unit has received the response packet;
The packet generation unit sets the packet transmission interval included in either the first packet or the second packet equal to the transmission interval adjusted by the transmission interval adjustment unit;
The transmitter transmits the first packet and the second packet at the adjusted transmission interval;
The terminal according to supplementary note 4, characterized by:

(Appendix 6)
A time synchronization system comprising a time server according to any one of Supplementary Notes 1 to 3 and a terminal according to Supplementary Notes 4 or 5.

(Appendix 7)
A reference time transmission step of acquiring a reference time from a timer unit that measures the reference time, and transmitting the acquired reference time to the terminal via the relay device;
A packet transmitted from the terminal at a predetermined transmission interval, and a first packet including a first packet including the transmission interval as a packet transmission interval, the transfer priority of the relay device being set to different priorities A packet receiving step of receiving two packets via the relay device;
A reception interval measuring step of measuring a reception interval indicating an interval from reception of the first packet to reception of the second packet;
A determination step of determining whether a difference between the packet transmission interval and the reception interval is within a predetermined range;
When it is determined that the difference is within a predetermined range, a response packet that is a response packet to the second packet and includes a response period that is a period from reception of the second packet to transmission of the response packet. A response packet generation step to generate,
A response packet transmission step of transmitting the generated response packet to the terminal via the relay device,
And a reference time transmission method.

(Appendix 8)
A reference time receiving step of receiving the reference time via a relay device from a time server that transmits the reference time;
A first packet and a second packet, which are packets to be transmitted to the time server, wherein the priority of transfer in the relay device is set to a different priority, and one of the packets includes a packet transmission interval indicating a mutual transmission interval A packet generation process for generating
A transmission step of transmitting the first packet and the second packet to the time server via the relay device in the order of their numbers at the transmission interval;
A response packet that is a response packet to the second packet and that receives a response packet including a response period that is a period from when the second packet is received until the response packet is transmitted from the time server via the relay device Receiving process;
A response waiting period measuring step of measuring a response waiting period indicating a period from when the second packet is transmitted to when the response packet is received;
Based on the reference time received from the time server, the measured response waiting period, and the response time acquired from the response packet, the time of the time measuring unit that measures time is synchronized with the reference time measured by the time server. A time setting step for setting to do,
A reference time setting method.

(Appendix 9)
A reference time is acquired from a timekeeping unit that measures a reference time with a time server, and the acquired reference time is transmitted to the terminal via the relay device, and received at the terminal,
A first packet and a second packet, which are packets to be transmitted to the time server, wherein the priority of transfer in the relay device is set to a different priority, and one of the packets includes a packet transmission interval indicating a mutual transmission interval Generating a packet in the terminal, and
A packet transmitting / receiving step of transmitting the first packet and the second packet from the terminal and receiving the packet by the time server;
A reception interval measurement step in the time server for measuring a reception interval indicating an interval from reception of the first packet to reception of the second packet;
A determination in the time server that determines whether a difference between the packet transmission interval included in either the received first packet or the second packet and the measured reception interval is within a predetermined range Process,
A response period that is a response packet to the second packet when the difference is determined to be within a predetermined range, and is a period from when the second packet is received until preparation for transmission of the response packet is completed Generating a response packet, and instructing to transmit to the terminal via the relay device, a response packet generating step in the time server,
In response to the instruction in the response packet generating step, the generated response packet is transmitted from the time server, and the response packet is transmitted and received at the terminal.
A response waiting period measuring step in the terminal for measuring a response waiting period indicating a period from when the second packet is transmitted until the response packet is received;
Based on the reference time received from the time server, the measured response waiting period, and the response time acquired from the response packet, the time server measures the time of the time measuring unit that measures time on the terminal side A time setting step in the terminal that is set to synchronize with a reference time,
A time synchronization method characterized by the above.

(Appendix 10)
On the computer,
A reference time transmission procedure for acquiring a reference time from a timer unit that measures the reference time, and transmitting the acquired reference time to the terminal via the relay device;
A packet transmitted from the terminal at a predetermined transmission interval, and a first packet including a first packet including the transmission interval as a packet transmission interval, the transfer priority of the relay device being set to different priorities A packet receiving procedure for receiving two packets via the relay device;
A reception interval measurement procedure for measuring a reception interval indicating an interval from reception of the first packet to reception of the second packet;
A determination procedure for determining whether a difference between the packet transmission interval and the reception interval is within a predetermined range;
When it is determined that the difference is within a predetermined range, a response packet that is a response packet to the second packet and includes a response period that is a period from reception of the second packet to transmission of the response packet. A response packet generation procedure to be generated;
A response packet transmission procedure for transmitting the generated response packet to the terminal via the relay device;
A program characterized by that.

(Appendix 11)
On the computer,
A reference time receiving procedure for receiving the reference time via a relay device from a time server that transmits the reference time;
A first packet and a second packet, which are packets to be transmitted to the time server, wherein the priority of transfer in the relay device is set to a different priority, and one of the packets includes a packet transmission interval indicating a mutual transmission interval A packet generation procedure for generating
A transmission procedure for transmitting the first packet and the second packet to the time server via the relay device in the transmission interval in the order of the numbers;
A response packet that is a response packet to the second packet and that receives a response packet including a response period that is a period from when the second packet is received until the response packet is transmitted from the time server via the relay device Receiving procedure,
A response waiting period measurement procedure for measuring a response waiting period indicating a period from when the second packet is transmitted to when the response packet is received;
Based on the reference time received from the time server, the measured response waiting period, and the response time acquired from the response packet, the time of the time measuring unit that measures time is synchronized with the reference time measured by the time server. And a time setting procedure for setting to
A program characterized by that.

10 time server 20 terminal 30 relay device 101 receiving unit 102 packet identifying unit 103 packet buffer 104 second packet buffer 105 reception time acquiring unit 106 reception interval measuring unit 107 timing unit 108 control unit 109 transmitting unit 110 packet information acquiring unit 111 reception time Information acquisition unit 201 Transmission unit 202 Reception unit 203 Operation unit 204 Display unit 205 Storage unit 206 Control unit 207 Timing unit 2061 Packet information acquisition unit 2062 Packet generation unit 2063 Response wait period acquisition unit 2064 Time setting unit

Claims (9)

A timekeeping section for measuring the reference time;
A reference time acquisition unit for acquiring a reference time from the time measuring unit;
A receiving unit for receiving various packets transmitted from the terminal via the relay device;
A transmission unit that transmits other various packets to the terminal via the relay device;
Packets transmitted from the terminal at a predetermined transmission interval, received by the receiving unit that is set to have different transfer priorities in the relay device and includes the transmission interval as a packet transmission interval. A packet identification unit for identifying the first packet and the second packet,
A packet information acquisition unit for acquiring information included in the received first packet and the second packet;
Based on the reception timing of the first packet and the second packet identified by the packet identification unit, the second packet reception time that is the reception time of the second packet is acquired, and the first packet is received. A reception time information acquisition unit for acquiring a reception interval indicating an interval from when the second packet is received;
A determination unit that determines whether a difference between the packet transmission interval acquired by the packet information acquisition unit and the reception interval acquired by the reception time information acquisition unit is within a predetermined range;
A reference time packet including the reference time acquired by the reference time acquisition unit is generated, a transmission instruction is issued to the transmission unit, and the determination unit determines that the difference is within the predetermined range. A response packet that is a response packet to the second packet, and includes a response period that is a period from the second packet reception time to the transmission of the response packet, and sends a transmission instruction to the transmission unit. A packet generation unit for outputting,
A time server characterized by this. The packet generation unit generates the reference time packet when the determination unit determines that the difference is within the predetermined range, and issues a transmission instruction to the terminal to the transmission unit.
The time server according to claim 1. The packet generation unit replaces the generation of the reference time packet by generating the response packet including the reference time.
The time server according to claim 2. A timekeeping section that keeps time,
A transmission unit that transmits various packets to the time server via the relay device;
A receiving unit for receiving various other packets from the time server via the relay device;
A packet having the time server as a transmission destination, a first packet including a packet transmission interval indicating a mutual transmission interval in either one of the packets, wherein the transfer priority in the relay device is set to a different priority. A packet generation unit that generates two packets and issues an instruction to the transmission unit to transmit the first and second packets in the order of their numbers;
From the packet received by the receiving unit, if the packet is a reference time packet that includes the reference time information, the type of the packet is identified, the reference time information included in the reference time packet is acquired, and the second packet A packet information acquisition unit that acquires information on a response period that is a period from reception of the second packet at the time server to transmission of the response packet included in the response packet when the response packet is a response packet; ,
A response waiting period measurement unit that measures a response waiting period that indicates a period from when the packet generation unit issues an instruction to transmit the second packet to when the packet information acquisition unit identifies the response packet; ,
A time setting unit that sets the time of the time measuring unit based on the reference time acquired by the packet information acquisition unit, the response period, and the response waiting period measured by the response waiting period measurement unit,
A terminal characterized by that. A transmission interval adjustment unit that adjusts the transmission interval according to whether the reception unit has received the response packet;
The packet generation unit sets the packet transmission interval included in either the first packet or the second packet equal to the transmission interval adjusted by the transmission interval adjustment unit;
The transmitter transmits the first packet and the second packet at the adjusted transmission interval;
The terminal according to claim 4. It is comprised with the time server which concerns on any one of Claims 1 thru | or 3, and the terminal which concerns on Claim 4 or 5.
A time synchronization system characterized by that. A reference time is acquired from a timekeeping unit that measures a reference time with a time server, and the acquired reference time is transmitted to the terminal via the relay device, and received at the terminal,
A first packet and a second packet, which are packets to be transmitted to the time server, wherein the priority of transfer in the relay device is set to a different priority, and one of the packets includes a packet transmission interval indicating a mutual transmission interval Generating a packet in the terminal, and
A packet transmitting / receiving step of transmitting the first packet and the second packet from the terminal and receiving the packet by the time server;
A reception interval measurement step in the time server for measuring a reception interval indicating an interval from reception of the first packet to reception of the second packet;
A determination in the time server that determines whether a difference between the packet transmission interval included in either the received first packet or the second packet and the measured reception interval is within a predetermined range Process,
A response period that is a response packet to the second packet when the difference is determined to be within a predetermined range, and is a period from when the second packet is received until preparation for transmission of the response packet is completed Generating a response packet, and instructing to transmit to the terminal via the relay device, a response packet generating step in the time server,
In response to the instruction in the response packet generating step, the generated response packet is transmitted from the time server, and the response packet is transmitted and received at the terminal.
A response waiting period measuring step in the terminal for measuring a response waiting period indicating a period from when the second packet is transmitted until the response packet is received;
Based on the reference time received from the time server, the measured response waiting period, and the response time acquired from the response packet, the time server measures the time of the time measuring unit that measures time on the terminal side A time setting step in the terminal that is set to synchronize with a reference time,
A time synchronization method characterized by the above. On the computer,
A reference time transmission procedure for acquiring a reference time from a timer unit that measures the reference time, and transmitting the acquired reference time to the terminal via the relay device;
A packet transmitted from the terminal at a predetermined transmission interval, and a first packet including a first packet including the transmission interval as a packet transmission interval, the transfer priority of the relay device being set to different priorities A packet receiving procedure for receiving two packets via the relay device;
A reception interval measurement procedure for measuring a reception interval indicating an interval from reception of the first packet to reception of the second packet;
A determination procedure for determining whether a difference between the packet transmission interval and the reception interval is within a predetermined range;
When it is determined that the difference is within a predetermined range, a response packet that is a response packet to the second packet and includes a response period that is a period from reception of the second packet to transmission of the response packet. A response packet generation procedure to be generated;
A response packet transmission procedure for transmitting the generated response packet to the terminal via the relay device;
A program characterized by that. On the computer,
A reference time receiving procedure for receiving the reference time via a relay device from a time server that transmits the reference time;
A first packet and a second packet, which are packets to be transmitted to the time server, wherein the priority of transfer in the relay device is set to a different priority, and one of the packets includes a packet transmission interval indicating a mutual transmission interval A packet generation procedure for generating
A transmission procedure for transmitting the first packet and the second packet to the time server via the relay device in the transmission interval in the order of the numbers;
A response packet that is a response packet to the second packet and that receives a response packet including a response period that is a period from when the second packet is received until the response packet is transmitted from the time server via the relay device Receiving procedure,
A response waiting period measurement procedure for measuring a response waiting period indicating a period from when the second packet is transmitted to when the response packet is received;
Based on the reference time received from the time server, the measured response waiting period, and the response time acquired from the response packet, the time of the time measuring unit that measures time is synchronized with the reference time measured by the time server. And a time setting procedure for setting to
A program characterized by that.

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