JP2012113504A - Communication terminal, control method and program thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication terminal capable of selecting a time server with high time accuracy as an acquisition destination of time information and not requiring a labor of a user.SOLUTION: A communication terminal 100 sends a response request packet through a network 300 and receives a response packet accordingly sent from time servers 200-206. Then, the communication terminal 100 selects a candidate for an acquisition destination of time information from among the time servers 200-206 using data acquired from the response packet. There is a reference source identifier showing a reference source for time adjustment of the servers 200-206 in the data acquired from the response packet, and the candidate for the acquisition destination of the time information is selected based on the reference source identifier.

Description

  The present invention relates to a communication terminal that performs time adjustment by network communication, a control method of the communication terminal, and a program.

  In recent years, there is a system that provides time information from a time server to a communication terminal by network communication using NTP (Network Time Protocol) to adjust the time of the communication terminal.

  In such a system, the time servers are usually hierarchized on the network, and the lower time servers refer to the upper time servers to adjust the time of the internal clock. For example, the time server of the second layer performs time adjustment with reference to the time server of the first layer. The time server of the first layer performs time adjustment of the internal clock by referring to the global positioning system (hereinafter referred to as GPS).

  The communication terminal acquires time information from any one of the hierarchical time servers and performs time adjustment. Patent Documents 1 and 2 disclose a method of selecting a time server from which time information is acquired.

In Patent Document 1, the IP address and priority of a time server are registered in a communication terminal.
The communication terminal selects a time server from which time information is acquired according to the priority order. Note that Patent Document 1 does not disclose a specific method for setting the priority order of time servers.

  In Patent Literature 2, the communication terminal makes a response request to the network by broadcast transmission, and selects a time server with a quick response as an acquisition destination of time information.

JP 2000-50004 A JP 2008-79008 A

  As time elapses, there is a delay or advance in the time measured by the internal clock of the time server. In the system in which the time servers are hierarchized, the time server of the first layer performs time adjustment at an accurate time by referring to the GPS or the like, and a time error occurs due to the passage of time after the time adjustment. The time server of the second layer refers to the time server of the first layer, and there is an error that has occurred in the time server of the first layer at the time when the time is adjusted. Further, in the time server of the second layer, the time lag occurs due to the passage of time after the time adjustment. As described above, the time server of each hierarchy has a time lag due to the passage of time, and this time lapse is taken over by the lower time server, so that the time accuracy of the lower time server may be lowered. .

  However, in Patent Documents 1 and 2, the time server from which the time information is acquired is selected without considering the difference in time accuracy. For this reason, there is a possibility that the time of the communication terminal is set by referring to a time server with low time accuracy.

  Further, in Patent Document 1, since it is necessary to register the priority order and IP address of the time server in advance in the communication terminal, it takes time and effort for the user.

  The present invention has been made in view of the above circumstances, and its purpose is to select a time server with high time accuracy as the acquisition source of time information, and for this selection, it takes time and effort to the user. It is to provide a communication terminal that is not required, a method for controlling the communication terminal, and a program.

A communication terminal according to the first aspect of the present invention provides:
A response request packet transmitter for transmitting a response request packet to a network to which a plurality of servers are connected;
A response packet receiving unit that receives a response packet from the server that has received the response request packet through the network;
A response packet data storage unit that stores data acquired from the response packet each time the response packet reception unit receives the response packet;
Using the data stored in the response packet data storage unit, a server selection unit that selects a candidate to obtain time information from the plurality of servers, and
As the data acquired from the response packet, there is a reference source identifier indicating a reference source of time adjustment of the server,
The server selection unit selects a candidate from which the time information is acquired based on the reference source identifier.

  Preferably, the response request packet transmitting unit transmits the response request packet to the network by broadcast transmission.

  Preferably, the server selection unit sets priorities of candidates from which the time information is acquired based on the reference source identifier.

Preferably, as the data acquired from the response packet, there is a synchronization identifier indicating whether or not the server is performing time synchronization,
The server selection unit sets priority of servers having different reference sources for time adjustment based on the reference source identifier, and sets priority of servers having the same reference source for time adjustment based on the synchronization identifier. It is characterized by setting.

Preferably, the plurality of servers are hierarchized on the network such that a lower layer server refers to an upper layer server for time adjustment,
As data acquired from the response packet, there is a layer value indicating a layer where the server is located,
The server selection unit, based on the hierarchy value, prioritizes candidates as the time information acquisition destination so that the upper layer server is selected as a time information acquisition destination in preference to the lower layer server. It is characterized by setting the order.

Preferably, a time required for the response packet receiving unit to receive the response packet after the response request packet transmitting unit transmits the response request packet, and after the server receives the response request packet. A delay time calculating unit that calculates a delay time indicating a difference from the time required to transmit the response packet;
The server selection unit is configured to set a priority order of candidates for obtaining the time information so that the server having a short delay time is preferentially selected as the obtaining source of the time information.

Preferably, the server further includes an internal processing time calculation unit that calculates an internal processing time required from when the response request packet is received until the response packet is transmitted,
The server selection unit sets priorities of candidates for obtaining the time information so that the server with a short internal processing time is preferentially selected as the time information obtaining destination. .

A communication terminal control method according to a second aspect of the present invention includes:
A response request packet transmission step of transmitting a response request packet to a network to which a plurality of servers are connected;
A response packet receiving step of receiving a response packet from the server that has received the response request packet through the network;
A response packet data storage step for storing data obtained from the response packet each time the response packet is received in the response packet reception step;
Using the data stored in the response packet data storage step, a server selection step of selecting a candidate to obtain time information from the plurality of servers, and
As the data acquired from the response packet, there is a reference source identifier indicating a reference source of time adjustment of the server,
In the server selection step, a candidate as an acquisition destination of the time information is selected based on the reference source identifier.

The program according to the third aspect of the present invention is:
Computer
Response request packet transmitting means for transmitting a response request packet to a network to which a plurality of servers are connected;
Response packet receiving means for receiving a response packet from the server that has received the response request packet through the network;
Response packet data storage means for storing data acquired from the response packet each time the response packet receiving means receives the response packet;
Using the data stored in the response packet data storage means, function as server selection means for selecting a candidate to obtain time information from the plurality of servers,
As the data acquired from the response packet, there is a reference source identifier indicating a reference source of time adjustment of the server,
The server selection unit selects a candidate from which the time information is acquired based on the reference source identifier.

  According to the present invention, a candidate as a time information acquisition destination is selected from a plurality of servers based on an identifier indicating a time reference source of the server. For this reason, it is possible to select a server with high time accuracy as the acquisition source of time information. Therefore, the time set by the communication terminal is accurate by adjusting the time of the communication terminal based on the time information acquired from the server.

  In addition, a candidate from which time information is acquired is selected using response packet data returned from the server. Therefore, since the time information acquisition source is selected, there is no need to input data into the communication terminal in advance. For this reason, a user's effort is not required.

It is a block diagram which shows the communication system with which the communication terminal which concerns on embodiment of this invention was applied. It is a block diagram which shows the physical structure of a communication terminal. It is a block diagram which shows the function structural example of a communication terminal. It is a figure which shows the example of a response request packet. It is a figure which shows the data used in order to select the acquisition source of time information. It is a figure which shows the example of a response packet table. It is a figure which shows the response packet table in which the data shown in FIG. 6 were rearranged by the server selection part. It is a figure which shows the response packet table in which the data shown in FIG. 7 were rearranged by the server selection part. It is a figure which shows the response packet table in which the data shown in FIG. 8 were rearranged by the server selection part. It is a figure which shows the example of a server selection table. It is a flowchart which shows an example of operation | movement of a communication terminal. It is a flowchart which shows an example of a response packet table storage process. It is a flowchart which shows an example of a response packet table rearrangement process. It is a flowchart which shows an example of a server selection table storage process. It is a figure which shows the other example of a response packet table. It is a figure which shows the response packet table by which data was rearranged by the server selection part. It is a figure which shows the other example of a server selection table. It is a figure which shows the other example of a server selection table. It is a block diagram which shows the other communication system with which the communication terminal of this invention is applied. It is a figure which shows the other example of a response packet table. It is a figure which shows the response packet table in which the data shown in FIG. 20 were rearranged by the server selection part. It is a figure which shows the response packet table in which the data shown in FIG. 21 were rearranged by the server selection part. It is a figure which shows the other example of a server selection table. It is a figure which shows the other example of a response packet table. FIG. 25 is a diagram illustrating a response packet table in which data illustrated in FIG. 24 is rearranged by a server selection unit. It is a figure which shows the response packet table in which the data shown in FIG. 25 were rearranged by the server selection part. FIG. 27 is a diagram illustrating a response packet table in which data illustrated in FIG. 26 is rearranged by a server selection unit. It is a figure which shows the response packet table in which the data shown in FIG. 27 were rearranged by the server selection part.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a block diagram showing a communication system 1 to which a communication terminal according to an embodiment of the present invention is applied. The communication system 1 includes a communication terminal 100, a plurality of time servers 200 to 206, and a network 300.

  The network 300 is a LAN (Local Area Network), and the communication terminal 100 and the time servers 200 to 206 can transmit and receive information through the network 300. The information includes time information using a network time protocol (hereinafter referred to as NTP).

  The time servers 200 to 206 periodically refer to other devices to correct the current time measured by the internal clock (hereinafter, correcting the time of the internal clock is referred to as “time adjustment” as appropriate). The time servers 200 to 206 are hierarchized on the network 300, and the lower time servers refer to the upper time servers for time adjustment.

  The time servers 200 to 202 are first layer time servers. The time server 200 periodically refers to the atomic clock 400 calibrated in accordance with national standards and performs time adjustment (the atomic clock transmits a pulse signal (Pulse-Per-Second (PPS)) every second. In 1, the atomic clock is indicated by “PPS”). The time server 201 periodically refers to a global positioning system (hereinafter referred to as GPS) 401 to perform time adjustment. The time server 202 performs time adjustment by periodically referring to a standard time supply system (hereinafter, telephone JJY) 402 using a telephone line.

  The time servers 203 to 205 are second layer time servers. The time servers 203 to 205 periodically request time information from any of the first layer time servers 200 to 202 via the network 300, and based on the time information returned in response to the request, Align. For example, the time server 203 requests time information from the time server 200 and adjusts the time based on the time information returned from the time server 200.

  The time server 206 is a third layer time server. The time server 206 requests time information from the time server 203 of the second layer through the network 300, and performs time adjustment based on the time information returned in response to the request.

  The time servers 200 to 206 are delayed or advanced in the time measured by the internal clock as time passes. The time servers 203 to 205 in the second layer carry over the time deviation that occurred in the time servers 200 to 202 in the first layer by the time adjustment with reference to the time servers 200 to 202 in the first layer. Later, a time lag will occur due to the passage of time. Further, the time tier 206 of the third tier takes over the time deviation caused by the time tier 203 of the second tier by the time adjustment with reference to the time server 203 of the second tier, and the time elapses after the time adjustment. This causes a time lag. From the above, the time servers 200 to 206 have lower time accuracy as the lower time servers.

  Further, the time accuracy of the time servers 200 to 202 in the first layer is determined from the accuracy of the time reference source, the time server 202 referring to the telephone JJY 402 → the time server 201 referring to the GPS 401 → the time server 200 referring to the atomic clock 400. It becomes higher in order.

  FIG. 2 is a block diagram illustrating a physical configuration example of the communication terminal 100. The communication terminal 100 includes a control unit 110, a storage unit 120, an input unit 130, an output unit 140, a communication control unit 150, and a time measuring unit 160.

  The storage unit 120 includes, for example, a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk, and the like. The storage unit 120 stores an operation program of the control unit 110 such as an NTP daemon program that is time synchronization software. The storage unit 120 functions as a work area for the control unit 110.

  The input unit 130 includes, for example, a keyboard and a mouse. The input unit 130 receives an operation by a user and supplies operation information to the control unit 110.

  The output unit 140 is composed of a display device or the like, for example. The output unit 140 provides output information to the user according to the control of the control unit 110.

  The communication control unit 150 includes a LAN port, a communication circuit, and the like. The communication control unit 150 is connected to the network 300 and transmits / receives data to / from other devices.

  The timer 160 has a built-in crystal oscillator, generates a clock pulse synchronized with the oscillation frequency of the crystal oscillator, and counts and outputs the current time in synchronization with the clock pulse.

  The control unit 110 includes a CPU (Central Processing Unit) and the like, and controls the operation of the entire communication terminal 100 according to a program stored in the storage unit 120. For example, the control unit 110 functions as a system clock that is a clock that operates as software in accordance with a program stored in the storage unit 120, and measures and outputs the current time. Further, the control unit 110 acquires time information from any of the time servers 200 to 206 according to the NTP daemon program, and corrects the current time measured by the time measuring unit 160 and the system clock.

  FIG. 3 is a block diagram illustrating a functional configuration example of the communication terminal 100. In communication terminal 100, control unit 110 executes processing according to a program, response request packet transmission unit 500, response packet reception unit 510, delay time calculation unit 520, internal processing time calculation unit 530, and response packet data storage. The unit 540 and the server selection unit 550 are configured.

  The response request packet transmitting unit 500 transmits a response request packet by broadcast transmission to the network 300 at the time of initial setting.

  FIG. 4 is a diagram illustrating an example of a response request packet. The response request packet is expressed in NTP and SNTP message formats. This message format is almost the same as the NTP message format described in RFC1305. In FIG. 4, the numbers in parentheses indicate the number of bits of each code included in the response request packet. For example, the number “2” of LI (2) indicates the number of bits of the synchronization identifier “LI (Leap Indicator)”. The codes of LI (2) to accuracy (8) are the values shown in the column immediately below. In the code below the route delay (32), the value of each bit is “0” unless otherwise specified.

  Since the response request packet is transmitted by broadcast, the destination is set to the broadcast address. The broadcast address is an address used for transmitting data to all devices connected to the network 300. For example, in class B, the private IP address of the network 300 is 172.16. XXX. XXX can be set, and 172.31.2555255 is the broadcast address. In class C, the private IP address of the network 300 is 192.168.48. XXX can be set, and 192.168.48.255 is the broadcast address. In the present embodiment, a class C broadcast address is used. In the response request packet, the port number of UDP (User Datagram Protocol) is set to 123.

  The time servers 200 to 206 return the response packet to the communication terminal 100 through the network 300 in response to receiving the response request packet. When the response request packet is broadcasted, the time servers 200 to 206 return the response packets all at once. The response packet receiving unit 510 (FIG. 3) receives the response packet sent back through the network 300 from when the response request packet transmitting unit 500 transmits the response request packet until a predetermined time elapses. The response packet is expressed in the message format shown in FIG. 4 like the response request packet.

  In the format shown in FIG. 4, the synchronization identifier “LI (Leap Indicator)” is an area used to indicate whether leap seconds are inserted or deleted in the last minute of the day. When leap second is inserted or deleted, 2-bit integers “01” and “10” are written in “LI”, respectively. In a normal case where no leap second is inserted or deleted, a 2-bit integer “00” is written in “LI”. “LI” is also an area used to warn that time synchronization is not performed. When time synchronization is not performed, 2-bit integer “11” indicating that time synchronization is not performed is written in “LI”.

  In the response request packet transmitted from the communication terminal 100, “LI” is set to a value of “00” as shown in FIG. Among the time servers 200 to 206, a time packet that is synchronized in time returns a response packet in which the value of “LI” remains “00”.

  On the other hand, a response packet in which the value of “LI” is changed to “11” is returned from the time server that does not synchronize the time. Due to the change of the “LI” value, the communication terminal 100 is notified that the time server does not synchronize the time.

  The “mode” is an area indicating a packet transmission source. In the response request packet, as shown in FIG. 4, “mode” is set to a value of a 3-bit integer “011” indicating the client. In the response packet, “mode” is changed to a value of a 3-bit integer “100” indicating the server.

  The “hierarchy” is an area indicating the class level of the local clock. In the response packet returned from the time servers 200 to 206, an 8-bit integer corresponding to the layer on the network 300 where the time servers 200 to 206 are located is indicated in “layer”. For example, in the response packet returned from the time servers 200 to 202, an 8-bit integer corresponding to the first layer is indicated.

  The “reference identifier” is an area in which a 32-bit integer corresponding to the time reference source of the time servers 200 to 206 is indicated. For example, the response packet returned from the time server 201 indicates a 32-bit integer corresponding to the GPS 401.

  The “start time stamp” is an area indicating a time T1 when the communication terminal 100 transmits a response request packet.

  The “reception time stamp” is an area in which time T2 when the time servers 200 to 206 receive the response request packet is indicated.

  The “transmission time stamp” is an area in which time T3 when the time servers 200 to 206 transmit the response packet is indicated.

  In the “start time stamp”, “reception time stamp”, and “transmission time stamp”, the times T1, T2, and T3 are expressed in a 64-bit time stamp format. The time T1 is, for example, the time measured by the time measuring unit 160 of the communication terminal 100. Times T2 and T3 are times measured by the internal clocks of the time servers 200 to 206.

  FIG. 5 is a diagram illustrating data used for selecting a time information acquisition source. (A) shows data acquired from the response packet of the time server 203. (B) shows data acquired from the response packet of the time server 201. (C) shows data acquired from the response packet of the time server 202. (D) shows data acquired from the response packet of the time server 200.

  In the present embodiment, data is acquired from the response packet in order to select a time information acquisition destination from the time servers 200 to 206. This data includes the IP address of the time servers 200 to 206 and the value of the hierarchy where the time servers 200 to 206 are located (hereinafter referred to as a hierarchy value).

  The data (A) includes the hierarchy value “2”. The layer value “2” indicates the second layer in which the time server 203 is located. The data of (B), (C), (D) includes the hierarchy value “1”. The layer value “1” indicates the first layer in which the time servers 201, 202, and 200 are located. The layer value is obtained from an 8-bit integer indicated in the “layer” of the response packet.

  The data acquired from the response packet also includes a reference source identifier indicating the time reference source of the time servers 200 to 206. The data of (A) includes the IP address “192.168.48.110” of the time server 200 as a reference source identifier indicating the time reference source (time server 200) of the time server 203. The data (B) includes a reference source identifier “GPS” indicating the time reference source (GPS 401) of the time server 201. The data of (C) includes a reference source identifier “TJJY” indicating the time reference source (telephone JJY 402) of the time server 202. The data of (D) includes a reference source identifier “PPS” indicating the time reference source (atomic clock 400) of the time server 200. These reference source identifiers are obtained from a 32-bit integer indicated in the “reference source identifier” of the response packet.

  The data acquired from the response packet includes the time T1 when the communication terminal 100 transmits the response request packet, the time T2 when the time servers 200 to 206 receive the response request packet, and the time servers 200 to 206 include the response packet. The time T3 at which is transmitted is also included. Times T1, T2, and T3 are obtained from a 64-bit integer indicated by a start time stamp, a reception time stamp, and a transmission time stamp.

  The delay time calculator 520 (FIG. 3) calculates the delay time P every time the response packet receiver 510 receives a response packet. The delay time P is calculated by Equation 1 using times T1, T2, and T3 acquired from the response packet and time T4 when the response packet is received by the communication terminal 100. The time T4 is acquired from the time measuring unit 160 of the communication terminal 100 when the response packet is received.

  The delay time P is the time (T4-T1) required for the response packet receiving unit 510 to receive the response packet after the response request packet transmitting unit 500 transmits the response request packet, and the time servers 200 to 206 This is a time indicating a difference from the time (T2−T3) required to receive the response packet after receiving the response request packet.

  The internal processing time calculation unit 530 calculates the internal processing time P every time the response packet reception unit 510 receives a response packet. The internal processing time P is calculated by Equation 2 using times T2 and T3 acquired from the response packet. The internal processing time P is a time (T3-T2) required for the time servers 200 to 206 to transmit a response packet after receiving the response request packet.

  The response packet data storage unit 540 acquires an IP address, a hierarchical value, and a reference source identifier (FIG. 5) from the response packet every time the response packet receiving unit 510 receives the response packet, and adds the delay time d and the data to these data. The internal processing time P is associated and stored in the storage unit 120.

  FIG. 6 is a diagram illustrating an example of a response packet table. The response packet table is created by storing data every time the response packet data storage unit 540 receives a response packet. In the response packet table, data (IP address / layer value / reference source identifier) included in each response packet is arranged in the order of reception, and each of these data is associated with a delay time d and an internal processing time P. .

  The server selection unit 550 uses the response packet table to select candidates from which the time information is acquired from the time servers 200 to 206, and sets the priorities of these candidates. This process is performed by the following first to fourth procedures. Hereinafter, a case where the response packet table of FIG. 6 is created will be described as an example.

  In the first to third procedures, the response packet table data is rearranged. In the first procedure, the data is rearranged so that data with a small hierarchical value is higher.

  FIG. 7 shows a response packet table in which the data shown in FIG. 6 is rearranged by the first procedure of the server selection unit 550. In the table of FIG. 7, the data (B, C, D) of the time servers 201, 202, and 200 having the hierarchy value “1” are arranged at the upper level, and the time servers 203, Data 205, 204 (A, E, G) are arranged. In addition, data (F) of the time server 206 whose layer value is “3” are arranged below.

  Next, in the second procedure, the data (B, C, D) whose layer value is “1” is rearranged based on the reference source identifier.

  FIG. 8 shows a response packet table in which the data shown in FIG. 7 is rearranged by the second procedure of the server selection unit 550. In the second procedure, the data (D) whose reference source identifier is “PPS” is placed at the top, the data (B) whose reference source identifier is “GPS” is located below it, and the reference source is below it. The data is rearranged so that the data (C) whose identifier is “TJJY” is located.

  Next, in the third procedure, the data in the response packet table is rearranged based on the delay time d and the internal processing time P.

  FIG. 9 shows a response packet table in which the data shown in FIG. 8 is rearranged by the third procedure of the server selection unit 550. The third procedure rearranges data having the same layer value and reference source identifier, and rearranges data so that data with a short delay time d is higher. When the table of FIG. 9 is compared with the table of FIG. 8, the order of the data E and G is reversed. This is because data E and G are both subject to reordering because the hierarchical value is “2” and the reference source identifier is “192.168.48.5”. Compared to the data G, the delay time d is longer, and the order is reversed. In addition, after the data is rearranged according to the delay time d, the data is rearranged so that the data with the shorter internal processing time P is higher if necessary. This rearrangement is necessary when the internal processing time P needs to be more important than the delay time d in order to determine the order of data. Specifically, in relation to the processing capability of the time server that has received the response request packet, when there is data having an extremely long internal processing time P in the response packet table, or when the hierarchical value and the reference source identifier are This corresponds to the case where there is data in which the internal processing time P differs by one digit or more in units of μ seconds compared to other data that is the same. In such a case, by rearranging the data based on the internal processing time P, it becomes possible to lower the priority of data having an extremely long internal processing time P. For example, when the response packet table is in the state of FIG. 9, when the data is rearranged so that the data with the short internal processing time P is higher, the response packet table returns to the state of FIG.

  In the table of FIG. 8, data C with a delay time d of 1900 μs is positioned above data A with a delay time d of 1800 μs. In the table of FIG. 9, the data C and A are arranged without changing the order from the table of FIG. This is because, unlike data C, there is no other data having a hierarchical value of “1” and a reference source identifier of “TJJY”, so that data C is subject to sorting in the third procedure. Because it was excluded from.

  Next, in the fourth procedure, a server selection table is created using the response packet table rearranged by the first to third procedures and stored in the storage unit 120.

  FIG. 10 is a diagram illustrating an example of a server selection table. In the server selection table, IP addresses included in the top n data of the response packet table are described. In the example of FIG. 10, the IP addresses included in the top 6 data are described in the response packet table of FIG. These IP addresses are arranged in the order of the response packet table of FIG. The server selection table in FIG. 10 indicates that the time servers 200 to 205 can be selected as time information acquisition sources. Also, the server selection table indicates the priority order for selecting the time server by the order of arrangement of IP addresses. In the table of FIG. 10, the priority order increases in the order of time server 205 → time server 204 → time server 203 → time server 202 → time server 201 → time server 200. This priority order is set as a result of data rearrangement according to the first to third procedures.

  That is, in the server selection table, the priority order of the time servers is set based on the reference source identifier by executing the second procedure. In the example of FIG. 10, according to the second procedure, the time servers 203 to 205 in the second layer whose reference source identifier is “IP address” → the time server 202 whose reference source identifier is “TJJY” → the reference source identifier is “ The priority is set in the order of the time server 201 that is “GPS” → the time server 200 that has the reference source identifier “PPS”.

  In the server selection table, the priority order is set based on the hierarchical value so that the upper time server is selected with priority over the lower time server by executing the first procedure. In the example of FIG. 10, the priority order is set to be higher in the order of the second layer time servers 203 to 205 and the first layer time servers 200 to 202 according to the first procedure.

  In the server selection table, the priority order is set so that a time server having a short delay time d or internal processing time P is preferentially selected by executing the third procedure. In the example of FIG. 10, the time server 204 having a delay time d of 4900 μsec (G in FIG. 9) is more than the time server 205 having a delay time d of 5000 μsec (E in FIG. 9) by the third procedure. , The priority is set higher.

  After the processing by the server selection unit 550, the NTP daemon is activated and the time of the time measuring unit 160 and the system clock is adjusted. Specifically, the time request packet is transmitted to the address indicated in the server selection table of FIG. With this transmission, time information indicating the time of the internal clock is returned from the time servers 200 to 206, and the time of the time measuring unit 160 of the communication terminal 100 is corrected to the time indicated by the time information.

  As shown in FIG. 10, when the server selection table includes a plurality of IP addresses, for example, a time request packet is transmitted to the highest IP address in the server selection table. Based on the returned time information, the time of the time measuring unit 160 and the like is corrected. In the example of FIG. 10, when a time request packet is transmitted to “192.168.48.110”, the time information is returned from the time server 200, and the time is corrected based on this time information. By doing in this way, the time alignment of the communication terminal 100 is performed based on the time information transmitted from the time server 200 with the highest time accuracy.

  Alternatively, the time request packet may be transmitted to all IP addresses in the server selection table or to the top n IP addresses. In this case, time information is returned from a plurality of time servers, and an average value of times indicated by these time information is calculated by a procedure according to NTP described in detail in RFC1305, and time is measured to the average value. The time of the part 160 etc. is corrected. In the example of FIG. 10, when time request packets are transmitted to all IP addresses, time information is returned from the time servers 200 to 205, and the time is corrected to an average value obtained from these time information.

  FIG. 11 is a flowchart illustrating an example of the operation of the communication terminal 100. The process shown in FIG. 11 is started, for example, when the user operates the input unit 130 (FIG. 2). When the NTP daemon is being activated, the NTP daemon is temporarily stopped by the user operation.

  First, the response request packet transmission unit 500 transmits a response request packet to the network 300 by broadcast transmission (step S101).

  Next, the response packet receiving unit 510 determines whether a response packet has been received from the time servers 200 to 206 (step S102).

  If it is determined that a response packet has been received (YES in step S102), a response packet table storage process is executed (step S103).

  FIG. 12 is a flowchart illustrating an example of a response packet table storage process.

  In this process, first, the delay time calculation unit 520 calculates the delay time d using the times T1 to T4 according to the above equation 1 (step S201).

  Next, the internal processing time calculation unit 530 calculates the internal processing time P using the times T2 and T3 according to the above equation 2 (step S202).

  Next, the response packet data storage unit 540 associates the delay time d and the internal processing time P with the data (IP address / layer value / reference source identifier) of the response packet (step S203) and stores them in the storage unit 120. (Step S204).

  Returning to FIG. 11, after step S103 is executed, or when it is determined in step S102 that a response packet has not been received (NO in step S102), the response packet receiving unit 510 responds in step S101. It is determined whether or not a predetermined time has elapsed since the request packet was transmitted (step S104).

  If it is determined that the predetermined time has not elapsed (NO in step S104), response packet receiving section 510 returns the process to step S102.

  By this return, step S103 is executed every time a response packet is received from the time servers 200 to 206. As a result, the response packet data is stored in the storage unit 120 in the order of reception, whereby the response packet table shown in FIG. 6 is created.

  If it is determined in step S104 that the predetermined time has elapsed (YES in step S104), a response packet table rearrangement process is executed (step S105).

  FIG. 13 is a flowchart illustrating an example of a response packet table rearrangement process. In this table rearrangement process, the first to third procedures by the server selection unit 550 described above are executed (steps S301 to S305). Through steps S301 to S305, the data in the response packet table is rearranged based on the layer value, the reference source identifier, the delay time d, and the internal processing time P.

  Returning to FIG. 11, after execution of step S105, server selection table storage processing is executed (step S106).

  FIG. 14 is a flowchart illustrating an example of the server selection table storage process. In the server selection table storage process, the fourth to fifth procedures by the server selection unit 550 described above are executed. First, in the response packet table in which the data is rearranged in the first to third procedures, IP addresses included in the top n data are acquired (step S401). Next, the IP address acquired in step S401 is stored in the storage unit 120 (step S402), and the server selection table shown in FIG. 10 is created and stored.

  Returning to FIG. 11, after step S106, the NTP daemon is restarted (step S107). By starting the NTP daemon, a time request packet is transmitted to the address shown in the server selection table (FIG. 10). Next, the time of the time measuring unit 160 is corrected based on the time information returned in response thereto.

  According to the present embodiment, a candidate that is a time information acquisition destination is selected from the time servers 200 to 206 based on an identifier or the like indicating the time reference source of the time servers 200 to 206. For this reason, it is possible to select a time server with high time accuracy based on the atomic clock 400, the GPS 401, the telephone JJY 402, or the like as the acquisition source of the time information, and based on the time information transmitted by these time servers. By adjusting the time of the communication terminal 100, the time measured by the communication terminal 100 becomes accurate.

  In addition, candidates for obtaining time information are selected using response packet data returned from the time servers 200 to 206. Therefore, it is not necessary to input data into the communication terminal 100 in advance in order to perform processing for selecting a time information acquisition destination. For this reason, a user's effort is not required.

  When the response request packet is transmitted to the network 300 by broadcast transmission, all of the time servers 200 to 206 connected to the network 300 transmit the response packet to the communication terminal 100. Therefore, it is possible to prevent a time server with high time accuracy from being excluded from candidates for the time information acquisition destination due to a response packet not being transmitted (response request packet not being received).

  Also, a priority order for selecting a time information acquisition destination is set based on a reference source identifier or the like. Therefore, by selecting the time information acquisition destination according to this priority, the time server 200 with high time accuracy is reliably referred to, and the time setting of the communication terminal 100 is performed. For this reason, the time measured by the communication terminal 100 becomes even more accurate.

  Further, the priority order is set based on the hierarchy value so that the upper time server is selected in preference to the lower time server. Therefore, the time of the communication terminal 100 is adjusted by referring to an upper time server with high time accuracy.

  In addition, the priority order is set so that a time server having a short internal processing time P or delay time d is selected with priority. As a result, a time server that responds quickly is selected as the time information acquisition destination, and therefore the time interval at which the communication terminal 100 refers to the time server to adjust the time is shortened. Therefore, the time measured by the time measuring unit 160 of the communication terminal 100 is such that the deviation due to the passage of time is suppressed to be small, which is advantageous in making the time of the time measuring unit 160 accurate at all times.

  The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims.

  For example, the communication terminal 100 may be configured to function as a time server that provides time information to other devices.

  Further, the response request packet may be transmitted to the network 300 by broadcast transmission periodically at an appropriate time interval other than at the time of initial setting. In this case, each time a new response packet is received, the data in the server selection table is updated.

  In addition, the candidates for the time information acquisition destination and the priority order for selecting the time information acquisition destination may be set based only on the reference source identifier. In this case, the delay time d and the internal processing time P are not calculated, and the response packet table created by the response packet data storage unit 540 is as shown in FIG. 15, for example.

  Then, the server selection unit 550 rearranges the data in the response packet table based on the reference source identifier. As a result, the data in the response packet table is as shown in FIG. 16, for example. In FIG. 16, data A, E, F, G with reference source identifier “IP address” → data C with reference source identifier “TJJY” → data with reference source identifier “GPS”. Data is rearranged so as to increase in the order of B → data D whose reference source identifier is “PPS”.

  Then, the server selection unit 550 acquires the top n IP addresses in the response packet table. As a result, for example, a server selection table shown in FIG. 17 is created. The table of FIG. 17 is obtained by acquiring the top three IP addresses of the response packet table. According to the table of FIG. 17, the time servers 200 to 202 having the atomic clock 400, the GPS 401, and the telephone JJY 402 as reference sources can be selected as time information acquisition sources. Further, the priority order of the time servers 200 to 202 is set so as to increase in the order of the time server 202 → the time server 201 → the time server 200.

  Further, the data in the server selection table can be transformed into the format shown in FIG. In the example of FIG. 18, data is written in the ntp.conf file format. The ntp.conf file is a setting file for the NTP daemon, which describes the specification of the time server to be referred to, the polling interval, the setting of access control, and the like, and optional parameters such as minpoll, maxpoll, and preference are added.

  FIG. 19 is a block diagram showing another communication system 2 to which the communication terminal of the present invention is applied. The communication system 2 is different from the communication system 1 of FIG. 1 in that the time reference source of the time server 200 is different, and the time server 200 refers to the GPS 401 and performs time adjustment periodically like the time server 201.

  When there are a plurality of time servers 200 and 201 having a common time reference source as in the communication system 2 of FIG. 19, the response packet table created by the response packet data storage unit 540 is shown in FIG. It becomes like this.

  In the table of FIG. 20, the reference source identifier “GPS” is shown in the data D and B of the time servers 200 and 201.

  Further, a synchronization identifier is associated with the IP address / reference source identifier. The synchronization identifier is obtained by acquiring a 2-bit integer of “LI” (FIG. 4) of the response packet, and indicates whether or not time synchronization is performed in the time servers 200 to 206.

  In the data B of the time server 201, the synchronization identifier “11” is indicated. This means that the time server 201 has not temporarily synchronized the time when transmitting the response packet.

  On the other hand, the synchronization identifier “00” is indicated in the data of other time servers (data other than B). This means that other time servers are performing time synchronization when transmitting the response packet.

  After the response packet table is created, the server selection unit 550 rearranges the data in the response packet table according to the following first and second procedures.

  First, in the first procedure, the data in the response packet table is rearranged based on the reference source identifier. As a result, the response packet table is as shown in FIG. 21, for example. In FIG. 21, data A, E, F, G with reference source identifier “IP address” → data C with reference source identifier “TJJY” → data with reference source identifier “GPS”. D → Higher in the order of data B whose reference source identifier is “GPS”.

  In the table of FIG. 21, the priority order of time servers with different reference sources for time adjustment is set based on the arrangement of the data. That is, the time servers 203 to 205 use other time servers as time reference sources, and the time server 202 and the time servers 201 and 200 use the telephone JJY 402 and the GPS 401 and 400 as time reference sources, respectively. Although the reference sources are different, in the table of FIG. 21, the priority is set in the order of time servers 203 to 206 → time server 202 → time servers 200 and 201.

  In the data B and D whose reference source identifier is “GPS”, the upper and lower positional relationships in FIG. 20 are inherited, and the data B is arranged higher than the data D as in FIG.

  Next, in the second procedure, the server selection unit 550 rearranges the data based on the synchronization identifier. This rearrangement targets data B and D having the same reference source identifier, and data D having a synchronization identifier “00” is higher than data B having a synchronization identifier “11”. Is done. As a result, the response packet table data is as shown in FIG.

  The table of FIG. 22 is set with the priority order of time servers having the same reference source for time adjustment based on the arrangement of data. That is, the priority order of the time servers 200 and 201 whose reference source for time adjustment is GPS 401 is set to be higher in the order of time server 201 → time server 200.

  Next, the server selection unit 550 acquires the top n IP addresses in the response packet table. As a result, for example, a server selection table shown in FIG. 23 is created. The table of FIG. 23 is obtained by acquiring the top three IP addresses of the response packet table. According to the table in FIG. 23, the time servers 200 to 202 with the GPS 401 or the telephone JJY 402 as a reference source can be selected as the time information acquisition destination. Further, the priority order for selecting the time servers 200 to 202 is set so as to increase in the order of the time server 202 → the time server 201 → the time server 200.

  According to the above processing, the priority order of the time servers having the same time synchronization reference source is set based on the synchronization identifier. For this reason, the time server performing time synchronization is selected with priority over the time server not performing time synchronization.

  Also, the priority order of time servers with the same time reference source and the priority order of time servers with different time reference sources are set together, so that the priority order of time servers with high time accuracy is set. , It can avoid being set low. That is, in the examples of FIGS. 20 to 22, the priority order is changed in the order of data A, E, F, G → data C → data B → data B, D as shown in FIG. Is set higher. In the second procedure, only the data B and D having the same reference source identifier are sorted and sorted based on the synchronization identifier. Therefore, as shown in FIG. 22, the data B and D whose reference source identifier is “GPS” are more than the data C, A, E, F, and G whose reference source identifier is “TJJY” and “IP address”. Don't be subordinate. As described above, it is possible to prevent the time server with high time accuracy from being excluded from the candidates for the time information acquisition destination because the time is not synchronized.

  Further, data rearrangement by the synchronization identifier (data rearrangement shown in FIGS. 15 to 16) and data rearrangement by the hierarchy value, the reference source identifier, and the delay time (data rearrangement shown in FIGS. 6 to 9). It is also possible to execute in combination. In this case, the response packet table created by the response packet data storage unit 540 is as shown in FIG. 24, for example. In the response packet table of FIG. 24, an IP address, a hierarchy value, a synchronization identifier, a reference source identifier, a delay time d, and an internal processing time P are associated with each other.

  First, the server selection unit 550 rearranges the response packet table data based on the hierarchy value. As a result, the response packet table is as shown in FIG. In FIG. 25, the data A, E, and G of the hierarchy value 2 are lower than the data B, C, and D of the hierarchy value 1, and the data F of the hierarchy value 3 is lower than the data A, E, and G of the hierarchy value 2. The data is rearranged so that

  Next, the server selection unit 550 rearranges the data whose layer value is “1” based on the reference source identifier. As a result, the response packet table is in the state shown in FIG. In FIG. 26, the data C whose reference source identifier is “TJJY” is rearranged below the data D whose reference source identifier is “GPS”.

  Next, the server selection unit 550 rearranges data having the same hierarchy value and reference source identifier based on the synchronization identifier. As a result, the response packet table is in the state shown in FIG. In FIG. 27, the data B with the synchronization identifier “11” is rearranged below the data D with the synchronization identifier “00”.

  Next, the server selection unit 550 rearranges the data in the response packet table based on the delay time d. As a result, the response packet table is in the state shown in FIG. In FIG. 28, the data E having the delay time d of “5000 μsec” is rearranged below the data G having the delay time d of “4900 μsec”.

  Thereafter, as described above, when it is necessary to place importance on the internal processing time P rather than the delay time d in order to determine the order of data, the data is rearranged based on the internal processing time P. Is called.

  The means and method for performing various processes in the communication terminal 100 of the present embodiment can be realized by either a dedicated hardware circuit or a programmed computer. The program may be provided by a computer-readable recording medium such as a flexible disk or a CD-ROM, or may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is normally transmitted to and stored in a storage unit such as a hard disk. The program may be provided as a single application software, or may be incorporated into the software of the device as one function of the device.

1, 2 Communication system
100 communication terminal
110 Control unit
120 storage unit
130 Input section
140 Output unit
150 Communication control unit
160 timers 200, 201, 202, 203,
204, 205, 206 Time server
300 network
400 Atomic clock (PPS)
401 GPS
402 Telephone JJY
500 Response request packet transmitter
510 Response packet receiver
520 Delay time calculator
530 Internal processing time calculator
540 Response packet data storage
550 server selector

Claims (9)

A response request packet transmitter for transmitting a response request packet to a network to which a plurality of servers are connected;
A response packet receiving unit that receives a response packet from the server that has received the response request packet through the network;
A response packet data storage unit that stores data acquired from the response packet each time the response packet reception unit receives the response packet;
Using the data stored in the response packet data storage unit, a server selection unit that selects a candidate to obtain time information from the plurality of servers, and
As the data acquired from the response packet, there is a reference source identifier indicating a reference source of time adjustment of the server,
The communication terminal characterized in that the server selection unit selects a candidate from which the time information is acquired based on the reference source identifier.   The communication terminal according to claim 1, wherein the response request packet transmission unit transmits the response request packet to the network by broadcast transmission.   3. The communication terminal according to claim 1, wherein the server selection unit sets priorities of candidates from which the time information is acquired based on the reference source identifier. As the data acquired from the response packet, there is a synchronization identifier indicating whether or not the server is performing time synchronization,
The server selection unit sets priority of servers having different reference sources for time adjustment based on the reference source identifier, and sets priority of servers having the same reference source for time adjustment based on the synchronization identifier. The communication terminal according to claim 3, wherein the communication terminal is set. The plurality of servers are hierarchized on the network such that a lower layer server refers to an upper layer server for time adjustment,
As data acquired from the response packet, there is a layer value indicating a layer where the server is located,
The server selection unit, based on the hierarchy value, prioritizes candidates as the time information acquisition destination so that the upper layer server is selected as a time information acquisition destination in preference to the lower layer server. The communication terminal according to any one of claims 1 to 4, wherein a rank is set. The time required for the response packet receiving unit to receive the response packet after the response request packet transmitting unit transmits the response request packet, and the response packet after the server receives the response request packet A delay time calculating unit that calculates a delay time indicating a difference from the time required to transmit
The server selection unit sets priorities of candidates as acquisition destinations of the time information so that a server with a short delay time is preferentially selected as an acquisition destination of the time information. Item 6. The communication terminal according to any one of Items 1 to 5. The server further includes an internal processing time calculation unit that calculates an internal processing time required from when the response request packet is received until the response packet is transmitted,
The server selection unit sets priorities of candidates for obtaining the time information so that the server with a short internal processing time is preferentially selected as the time information obtaining destination. The communication terminal according to any one of claims 1 to 6. A response request packet transmission step of transmitting a response request packet to a network to which a plurality of servers are connected;
A response packet receiving step of receiving a response packet from the server that has received the response request packet through the network;
A response packet data storage step for storing data obtained from the response packet each time the response packet is received in the response packet reception step;
Using the data stored in the response packet data storage step, a server selection step of selecting a candidate to obtain time information from the plurality of servers, and
As the data acquired from the response packet, there is a reference source identifier indicating a reference source of time adjustment of the server,
In the server selection step, a candidate for obtaining the time information is selected based on the reference source identifier. Computer
Response request packet transmitting means for transmitting a response request packet to a network to which a plurality of servers are connected;
Response packet receiving means for receiving a response packet from the server that has received the response request packet through the network;
Response packet data storage means for storing data acquired from the response packet each time the response packet receiving means receives the response packet;
Using the data stored in the response packet data storage means, function as server selection means for selecting a candidate to obtain time information from the plurality of servers,
As the data acquired from the response packet, there is a reference source identifier indicating a reference source of time adjustment of the server,
The server selecting means selects a candidate from which the time information is acquired based on the reference source identifier.

Images