JPS6071981A - Remote time setting system - Google Patents

Abstract

PURPOSE:To report the correct time from one device to the other by executing transmission of a command plural times and calculating an average elapsed time on a basis of the elapsed time of this execution and comparing this calculated time with a propagation time obtained in accordance with a stored time. CONSTITUTION:When receiving a response, a transmitting part 12 of a command 1 refers to a clock 10 in a device A1 immediately to obtain the time elapsed from the time which is stored when the command 1 is transmitted. The command transmitting part 12 measures the time spent in transmission of the command 1 and reception of the response repeatedly plural times, and an arithmetic average value is calculated in an average value calculating part 13. A transmitting part 14 of a command 2 defines the half value of the received average value as a propagation delay time T of a communication line 3. The clock 10 in the device A1 is referred to obtain the time spect in trasnmission of the command 2 and reception of the response, and this time is defined as t1'. Values t1' and T/2 are compared with each other; and if they are equal to each other, the processing is completed, and the same time is set to a clock 11 and the clock 10.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention relates to a control method for setting the time from one device to a clock in another device in a communication system, for example, a communication network. be.

(b) Prior Art and Problems In a system in which multiple devices, such as computers and terminals (9) communication control devices, are connected via communication channels to form two communication networks, each device must have a clock that indicates the same time. is often necessary. For example, when storing a history of transmitted and received data in a device, it is necessary to store the time at which the data was transmitted or received. This time is typically stored by reference to a clock within the device. When analyzing the history of transmitted and received data later, the time stored between each device must be used.

Generally, after each device is turned on and started up, it is necessary to reset the time on the device's internal clock, and conventionally this has been done by the operator of each device by referring to the time on an external clock. As systems become more automated, if an operator sets the time on the clock in one device, the time can be set on the clocks in other devices from a remote location through the communication path connecting the devices. This is now done through communication between devices. However, the conventional method in which the current time is notified from a remote location to another device through a communication path, and the device that receives the time sets the time as it is in its internal clock, has the following problems.

When a satellite communication line is used as a communication channel, there is a difference between the actual time and the set time due to the propagation delay of the line. This deviation is, for example, a value of about 0.3 seconds. Furthermore, in order to generally notify the time to another device, the current time is sent to the other device using a transmission control procedure that is often used in data communications. At that time,
If an error occurs in the data carrying the time due to noise or the like on the communication line, the same data is retransmitted from the transmitter side according to the error recovery control method determined in the transmission control procedure. This retransmission control is not conscious of transmission control. When data is retransmitted, a delay that is two to three times the communication line delay occurs in the control process. Therefore, the time set on other devices will differ from the current time.

(C) Purpose of the Invention The purpose of the present invention is to transmit the correct time from one device even when devices are connected by a communication line with a large transmission delay, or when error retransmission control is performed due to an error in the communication line. The purpose is to notify other devices so that they can be set as their clocks.

(d) Structure of the Invention In order to achieve the above object, the present invention includes a first device having a clock unit that can directly set a reference time as a system, and a clock unit to which the reference time is not directly set. In a communication system in which a single or a plurality of second devices are connected by a communication path, the first device includes command 1 transmitting means for sending a first command to the second device; a first time storage means for storing the time when the first command is transmitted by referring to a clock section within the own device; means for calculating the elapsed time based on the current time in the clock section and the time stored in the first time storage means; an average value calculation unit that calculates an average elapsed time value for a plurality of elapsed times within a predetermined range among the plurality of elapsed times determined by the command 1 sending means; command 2 transmitting means for transmitting to the second device a second command including time information obtained by adding 1/2 of the average elapsed time to the current time obtained from the hour hand section in the device; a second time storage means for storing the time when the command was sent by referring to a clock section within the own device; a comparison means for calculating the propagation time based on the current time in the clock section and the time stored in the second time storage means and comparing it with the average elapsed time, and a difference between the two times as a result of the comparison; means for repeatedly transmitting the second command when the second command is not within a predetermined range; and means for transmitting a response to the first command to the second device. and a command 2 receiving unit that, when receiving the second command, sets the time information included in the command in a clock unit in the device itself and sends a response to the command. Additionally, the system is characterized in that the time is set in a clock section in each device in the system.

(e) Examples of the invention Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of a communication system according to an embodiment of the present invention;
FIG. 2 is a diagram showing the operation sequence of the embodiment.

In Figure 1, ■ is the device A where the reference time is directly set.
, 2 is device B whose time is set based on information from device A.
, 3 is a communication circuit, 4 and 5 are transmission control units, 6 and 7 are time management units, 8 and 9 are transmission control interface units, 10 and 11
is a clock, 12 is a command 1 transmitter, 13 is an average value calculation unit, 14 is a command 2 transmitter, 15 is a command I receiver,
16 is a command 2 receiving section.

In the embodiment of FIG. 1, two devices (eg, computers, terminals, etc.), a device At and a device B2, are connected by a communication line 3 having a constant delay time T seconds. Both device At and device B2 have a transmission control section 4.5 and time management sections 6 and 7 inside.

The transmission control unit 4.5 controls transmission control procedures for correctly transmitting and receiving data. The time management section 6.7 has a clock 10.11 for indicating the current time. The time setting for the clock 10.11 is performed in the device A1 by an external operator's operation, and in the device B2 by a time notification from the device A1 through the communication line 3. Here, a control method will be described in which the device A1 notifies the device B2 of the time and sets the clock 11 in the device B2 to the same time as the clock 10 in the device AI.

The time management unit 6 in the device Al has a clock 10. Command 1 transmitter 12. Command 2 transmitter 14. Average value calculation unit 13.
The time management section 7 in the device B2, which is composed of the transmission control interface section 8, includes a clock 11, a command l receiving section 15.
A clock 10 in the apparatus Al, which is composed of a command 2 receiving section 16 and a transmission control interface section 9, is set to the correct time by an external operation. The correct time is not set on the clock 11 in device B2.

The command 1 transmitter 12 of the device AI transmits the command 1 to the device B2. The command 1 transmitter 12 refers to the clock 10 in the device AI and stores the time when transmitting the command 1. Command 1 is transmitted from the transmission control interface section 8. in the device Al. After passing through the transmission control unit 4, it is sent to the device B2 through the communication line 3. In device B2, command 1
is the transmission control unit 5. The command is passed through the transmission control interface section 9 to the command 1 receiving section 15. Command receiving unit 1
5 immediately sends a response upon receiving command 1. This response goes through the opposite route to command 1,
The command is passed to the command 1 transmitter 12 of the device A1. Upon receiving the response, the command 1 transmitter 12 immediately refers to the clock 10 in the device Al and measures the elapsed time from the time stored at the time of command 1 transmission. This round trip time is
2 of the propagation delay time of communication line 3 from 1 to device B2
Equivalent to twice as much. Let this value be tl. Furthermore, the command 1 transmitter 12 repeats measurement of the round trip time by transmitting the command 1 multiple times, and sets each round trip time to tl ---t n. Generally, each value from tl to tn has some variation. The command 1 transmitter 12 is
The values of tl, tz, -tn are passed to the average value calculation unit 13. The average value calculation unit 13 receives the received 11°jz, ---t
Among n, those with values that are particularly different from others, for example, those with values that are twice or more, are excluded, and the arithmetic mean value of the remaining values is calculated. Here, the ones with particularly large values are device A1 and device B2.
This is based on the result of retransmission control based on the transmission control procedure between the transmission control units. Therefore, it is different from a simple round trip time.

The average value calculation section 13 passes the requested average value to the command 2 transmission section 14. The command 2 transmitter 14 sets the received average value 2 as the propagation delay time T of the communication line 3 between the device At and the device B2. Command 2 is for setting the time designated by device AI in the clock in device B2, and the value of the time to be set is entered in a predetermined portion of command 2. When transmitting the command 2, the command 2 transmitter 14 refers to the clock 10 in the device Al, stores the value, and enters the time 1 which is T seconds ahead of that time into the predetermined part of the command 2. Send such command 2 to device B2. Command 2 is transmitted through the transmission control interface section 8.transmission control section 49 communication line 3. of the device AI. Transmission control unit 5 of device B2. The command 2 is passed through the transmission control interface section 9 to the command 2 receiving section 16.

Upon receiving the command 2, the command 2 receiving unit 16 immediately sets the time entered in the predetermined part of the command 2 to the clock 11 in the device B2, and returns a response to the command 2 to the device A1. . This response is passed to the command 2 transmitter 14 through the reverse route to the command 2. Upon receiving the response, the command 2 transmitter 14 immediately refers to the clock 10 in the device AI, and determines the round trip time corresponding to the command 2 as tl' based on the difference from the time stored at the time of transmitting the command 2.

The values of tl' and TX2 are compared, and if they are not equal, the process is completed. If there is a large difference, it means that the propagation delay time on the communication line 3 has changed abnormally compared to normal when sending and receiving the command 2 and its response. This delay also includes retransmission 2 control by the transmission control procedure. If the values of tz' and TX2 are significantly different, command 2 is transmitted again. The operations at this time are the same as those for the first transmission of command 2 for both device At and device B2. The transmission of command 2 is repeated until tn' becomes approximately equal to the value of TX2. When the values of tn' and TX2 become approximately equal, the clock 11 in device B2 is set to the same time as the clock 10 in device Al.

In the above operations, the processing time within the device from referencing or setting the clock to sending command 1.2 or its response is sufficiently short compared to the time accuracy in devices AI and B2. shall be taken as a thing. In addition, the time setting operation is performed when no other data transmission/reception is being performed within the device, and the transmission control units 4 and 5 use commands 1 and 2.
To prevent emails and responses from being queued and having to wait.

Further, if the propagation delay time between device A1 and device B2 is known in advance, the operation using command 1 is not performed, and only the operation using command 2 is sufficient.

(F) By using a method that exceeds the effects of the invention, even when devices are connected by a communication line with a large transmission delay, or when error retransmission control is performed due to an error in the communication line, the correct time can be transmitted from one device to another. device and set it as the clock on other devices.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a communication system according to an embodiment of the present invention;
FIG. 2 is a diagram showing the operation sequence of the embodiment. In FIG. 1, l is the device A where the reference time is directly set.
, 2 is device B whose time is set based on information from device A.
, 3 is a communication line, 4 and 5 are transmission-based transmission units, 13 is an average value calculation unit, 14 is a command 2 transmission unit, 15 is a command 1 reception unit, and 16 is a command 4 transmission unit.

Claims (1)

[Claims] A first device having a clock section that can directly set a reference time as a system and a single or plural second devices having a clock section to which the reference time cannot be directly set are connected by a communication path. In the communication system, the first device includes command 1 sending means for sending a first command to the second device, and a clock unit in the device to record the time when the first command is sent. a first time storage means for referencing and storing; and upon receiving a response from the second device to the first command, a current time in a clock section within the device itself and storage in the first time storage means; a command 1 transmitter having a means for calculating an elapsed time based on the time at which the command 1 is transmitted; and a means for calculating a plurality of elapsed times by executing the transmission of the command 1 a plurality of times; and the command 1 transmitting means. an average value calculation unit that calculates an average elapsed time value for a plurality of elapsed times within a predetermined range out of the plurality of elapsed times determined by the above average elapsed time; a command 2 transmitting means for transmitting a second command including time information with a value of /2 added to the second device, and a clock unit in the own device to check the time when the second command is transmitted; and a second time storage means for storing the current time in the hour hand section of the own device when a response from the second device to the second command is received. a comparison means for calculating the propagation time based on the time at which the propagation time is passed and comparing it with the average elapsed time; a command 2 transmitter having means for repeatedly executing the command; a command 1 receiver having means for transmitting a response to the first command to the second device; and when receiving the second command; It is equipped with a command 2 receiving section that sets the time information included in the command in the clock section in its own device and sends a response to the command, and sets the time in the clock section in each device in the system. A remote time setting method characterized by the following configuration.