JP2633499B2 - Network time synchronization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network time synchronization system, and more particularly to a network time synchronization system for performing time synchronization processing and maintenance management of time correction data in parallel with normal data transmission and reception.

[0002]

2. Description of the Related Art As a conventional network time synchronization method for synchronizing clocks provided in respective nodes in a communication network so as to indicate a common time, for example, an "an election algorithm is a distributed clock synchronization." An Election Algorithm for a DistributedC
lock Synchronization Program) ”(Proceedings of th
e 6th International Conference on DISTRIBUTED COMP
UNIX introduced in UTING SYSTEM, p.364-371)
There is TEMPO on Operating System 4.3BSD.

[0003] In this system, one node becomes a master, and this master node inquires of all nodes at predetermined time intervals for time, and each node sent to the master node in response to the inquiry. Calculate the average time based on the time. Thereafter, the master node instructs all the nodes to adjust the clock provided in each node, and each node adjusts according to the instruction so that the clock indicates this average time.

A conventional network time synchronization method will be described with reference to FIG.

A conventional network time synchronization method is shown in FIG.
As shown in (1), a time collection processing unit 44 for performing time collection requests and time data collection for the time synchronization devices 5-1 to 5-3 in each node other than the master node, A clock processing unit 43 for determining the time of the network, and a time distribution processing unit 45 for transmitting the determined synchronization time of the network via the transmission / reception unit 47
Time supply device 4 provided in the master node having
A clock processing unit 55 for reading the value of the local clock 57; a time transmission processing unit 52 for transmitting the read time via the transmission / reception unit 51; It comprises time synchronizing devices 5-1, 5-2 and 5-3 provided in each node other than the master node having a time receiving processing unit 53 for requesting time setting.

The time collecting unit 44 of the time supply device 4
A time request data is transmitted to each of the time synchronizers 5-1, 5-2, and 5-3 on the network at regular time intervals to make a time collection request. The time reception processing unit 53 of the time synchronization device 5-1 that has received the time collection request instructs the clock processing unit 55 to read the local clock 57, and the time transmission processing unit 52 transmits this time via the transmission / reception unit 51. To the time supply device 4. The time synchronizers 5-2 and 5-3 similarly transmit their own time based on the time collection request from the time supply device 4.

[0007] The time collecting unit 44 includes a time synchronizing device 5-1.
Time data and time supply device 4 collected from .about.5-3
The average value is obtained from the time data of the master node obtained from the clock processing unit 43 to determine the synchronization time in the network, and the clock processing unit 43 is instructed to set the system clock 42 based on the synchronization time.

[0008] The time collecting unit 44 includes a clock processing unit 43.
At the same time as issuing the time setting instruction to the time distribution unit 45, the time distribution processing unit 45 is instructed to deliver the synchronization time and transmit the time. The time distribution processing unit 45 transmits the delivered synchronization time to each of the time synchronization devices 5-1 to 5-3 via the transmission / reception unit 47.

The time reception processing unit 53 of the time synchronization device 5-1
When the synchronization time is received from the time supply device 4, the synchronization time is delivered to the clock processing unit 55, and the clock processing unit 55 recognizes this synchronization time as the latest time of the time synchronization device 5-1 and sets the local clock 57. I do.

As described above, the synchronization time on the network is determined by the time supply device 4 collecting time data of all the systems on the network and obtaining an average time.

The determined synchronization time is simultaneously distributed to each time synchronization device, and a new time is set for the local clock of each time synchronization device based on the synchronization time.

In the above-mentioned conventional network time synchronization method, no consideration is given to the transmission time in the communication line between the master node and the other nodes. 63-52
No. 089 and JP-A-3-264890.

According to these techniques, when time synchronization is performed, a local clock notification signal is transmitted from a time supply device in the master node to a time synchronization device in a node other than the master node. After returning the reception response signal to the time supply device, the delay error due to the data transfer is calculated, and the time data as a result of performing the time correction process for the time synchronization device is transmitted to the time synchronization device. Synchronization of the local clock of the synchronizer is being performed. Such a synchronization process is performed for each time synchronization device in each node.

[0014]

In the conventional network time synchronization method described above, the synchronization time is determined as the average value of the time of all nodes including the master node, and the clocks of all the nodes including the master node are synchronized with each other. In the method of updating to the time, the accuracy of the clock of the time synchronization in the network includes the variation of the accuracy of the clock of all nodes and the error of the delay time due to the collection and transmission of the time data, and the clock of the network There is a disadvantage that accuracy is deteriorated.

Further, the above-mentioned Japanese Patent Application Laid-Open No. 63-52089 and Japanese Patent Application Laid-Open No. 3-2, each of which corrects the delay of a communication line.
In the network time synchronization method described in Japanese Patent Application Laid-Open No. 64890, a single synchronization process in one node requires three flows of data on a transmission line, and when there are many nodes on the same network, However, there is a disadvantage in that the amount of data on the network increases, causing data delay.

Further, since data transmission / reception for time synchronization processing is designed separately from normal data transmission / reception processing, there is a disadvantage in that the number of software development steps related to transmission / reception increases.

An object of the present invention is to carry out batch maintenance of time correction data for a local clock at a master node and to perform transmission and reception of time data for time synchronization processing into ordinary data transmission and reception so as to realize a network clock. Can significantly improve the synchronization accuracy of the network, suppress the increase in the amount of data on the network due to the synchronization process, and
An object of the present invention is to provide a time synchronization method for a network with a small number of development steps.

[0018]

According to a first aspect of the present invention, there is provided a time synchronization system for a network, wherein a time supply device provided in a master node and a time synchronization device provided in a plurality of nodes other than the master node are connected by a network. In the time synchronization method of a connected network, the time supply device includes a first time generation unit configured to generate a reference time of the master node, a time reading unit configured to read a time of the first time generation unit, A correction value storage unit that stores a correction value used for creating time data for synchronization processing for each node; and a data transmission processing unit that creates transmission data incorporating the time data for synchronization processing when transmitting data. ,
First transmission / reception means for transmitting / receiving data to / from each of the nodes, and response reception processing means for performing a reception process of reception data from each of the nodes and extracting response time data and a source node address in the reception data And reading a correction value corresponding to a data transmission destination node address from the correction value storage means, adding the correction value to the latest first reference time of the first time generation means supplied from the time reading means, and performing synchronization processing. Time data is generated and supplied to the data transmission processing means, the response time data supplied from the response reception processing means, and the latest second reference of the first time generation means supplied from the time reading means. A correction value management process for calculating a new correction value and updating the correction value storage means when it is necessary to correct the correction value from the time And a plurality of time synchronization devices, each of which includes a second transmission / reception means for transmitting / receiving data to / from each of the nodes including the master node; a reception / transmission unit for receiving data; Data reception processing means for extracting processing time data;
Second time generating means for generating a reference time of the own node;
A new time is set in the second time generating means based on the synchronization processing time data supplied from the data receiving processing means, and the latest time of the second time generating means is read out in response to a request. It is provided with time setting reading means for supplying as data, and response transmission processing means for creating response transmission data to the master node including the supplied response time data.

A network time synchronization method according to a second invention is the network time synchronization method according to the first invention, wherein the correction value is corrected by adding the correction value to a second reference time and response time data. And a correction value management processing unit that sets a value obtained by adding one half of the difference to the correction value to a new correction value.

The time synchronization method for a network according to a third invention is the time synchronization method for a network according to the first invention, wherein the correction value is corrected by adding the correction value to the second reference time and response time data. And a correction value management processing unit that sets a value obtained by adding a quarter of the difference from the correction value to the correction value as a new correction value.

[0021]

Next, a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a network time synchronization system according to the present invention.

As shown in FIG. 1, the network time synchronization system of the first embodiment includes a time supply device 1 provided in a master node and a time synchronization device 2 provided in a plurality of nodes other than the master node. 1-2 is network 3
Connected by

The time supply device 1 provided in the master node includes a system clock 12 for generating a reference time of the master node, a clock processing unit 13 for reading the time of the system clock, and time data generation for synchronization processing. A correction value management table 17 storing correction values used for each node, a data transmission processing unit 11 for creating transmission data incorporating time data for synchronization processing at the time of data transmission, Transmission / reception unit 1 for sending and receiving
And a response reception processing unit 16 that performs a process of receiving data received from each node and extracts response time data and a source node address in the received data.
And a correction value corresponding to the data transmission destination node address from the correction value management table 17 and read the clock processing unit 1.
3 is added to the latest reference time supplied from 3 to generate time data for synchronization processing, supplied to the data transmission processing unit 11, supplied from the response reception processing unit 16 and supplied from the clock processing unit 13. When the correction value needs to be corrected from the latest reference time, a correction value management processing unit 14 that calculates a new correction value and updates the correction value management table 17 is included.

On the other hand, a time synchronizer 2-1 provided in a node other than the master node includes a transmission / reception unit 21 for transmitting and receiving data to and from each node including the master node, a reception data reception process and a reception process. A data reception processing unit 22 that extracts synchronization processing time data from the data, a local clock 24 that generates a reference time of the node, and a new local clock 24 based on the synchronization processing time data supplied from the data reception processing unit 22. The clock processing unit 23 reads the latest time of the local clock 24 in response to a request and supplies it as response time data, and a response that creates response transmission data to the master node including the supplied response time data The transmission processing unit 25 is included.

The time required from reading the reference time of the system clock 12 of the time supply device 1 of the master node to setting the value to the local clock 24 of the time synchronizer 2-1 in the node (this is the data delay). Is equivalent to Δt, the time data for synchronization processing is the latest reference time T read from the system clock 12.
If 0 is added and corrected by Δt before transmission, the time (T0
+ Δt), the time supply device 1 and the time synchronization device 2-1
And can be synchronized. That is, in order to achieve synchronization, a correction corresponding to this delay time is necessary, and since this delay time differs from node to node, a correction value used to create time data for synchronization processing is stored in the master node for each node. The correction value management table 17 is prepared.

The correction value is obtained by sending time data for synchronization processing from the master node to another node to set the time of the local clock of the node, and the response time data sent from this local clock is used as the master node. The correction value management processor 14 determines and corrects the turnaround time with reference to the turnaround time until the arrival at. For example, the transmission time of the synchronization processing time data from the master node is set to T0.
Assuming that the time at which the response time data arrives at the master node is T1, the correction value for the node is Δt = (T1 -T0).
/ 2. When a response is made with a delay of time τ without immediately responding at the node, a correction value (Δτ) / 2 for correcting the synchronization shift time Δτ of the local clock 24 corresponding to the time τ is added. But this amount is insignificant.

Next, a time synchronization operation between the time supply device 1 and the time synchronization device 2-1 will be described as an operation of the first embodiment with reference to FIG.

Initially, the correction value management table 17 is in an initial state, and no data is stored.

The system clock 12 generates the reference time of the master node.
Time synchronization processing is performed on nodes other than the master node using the time at which the
Means that the reference time of the network has been generated,
Extremely high precision is required.

When the master node requests data transmission to a node provided in the time synchronization device 2-1, the data transmission processing unit 11 notifies the correction value management processing unit 14 of the transmission destination, and the transmission destination is Requests supply of time data for synchronous processing used when performing synchronous processing.

In response to this, the correction value management processing unit 14 requests the clock processing unit 13 to supply the latest time data of the system clock 12, and the clock processing unit 13 reads the latest time data T0 of the system clock 12 and Is supplied to the correction value management processing unit 14, the correction value management processing unit 1
4 reads out a correction value (.DELTA.t: 0 at the beginning) for the transmission destination from the correction value management table 17 and adds it to T0 to calculate time data for synchronization processing (T0 + .DELTA.t). Supply this.

The data transmission processing section 11 incorporates the time data for synchronization processing into the transmission data, creates transmission data in a fixed format, and supplies the transmission data to the transmission / reception section 15, which transmits and receives the transmission data via the network 3. The data is transmitted to a certain transmission destination node of the time synchronization device 2-1.

The time synchronization device 2 in the transmission destination node
The first transmission / reception unit 21 receives the transmitted data and supplies it to the data reception processing unit 22.

The data reception processing section 22 processes the supplied reception data, reads out the synchronization processing time data contained therein, and supplies it to the clock processing section 23, and the clock processing section 23 supplies the supplied synchronization processing time. The time of the local clock 24 is newly set to the time indicated by the data, that is, (T0 + Δt).

The time synchronization device 2 is operated by the above-described synchronization processing operation.
-1 indicates that synchronization with the time supply device 1 in the master node has been achieved. Since Δt = 0 only at the beginning, the transmission delay is not corrected and the time lag remains.

The operation to be performed thereafter is a correction value management processing operation for checking whether or not the correction value is appropriate, and correcting it if it is not appropriate.

When the time synchronization device 2-1 makes a response to the received data, the response transmission processing unit 25 requests the clock processing unit 23 to supply the latest time data of the local clock 24 as response time data. When the clock processing unit 23 reads the latest time data T of the local clock 24 and supplies it to the response transmission processing unit 25 as response time data accordingly, the response transmission processing unit 25 incorporates the response time data into the response data. The response data in a certain format is created and supplied to the transmission / reception unit 21. The transmission / reception unit 21 transmits this to the master node having the time supply device 1 via the network 3.

The transmission / reception unit 15 of the time supply device 1 in the master node receives the transmitted data and supplies it to the response reception processing unit 16.

The response reception processing unit 16 processes the supplied reception data, reads out the response time data and the transmission destination in the received reception data, and reads the response time data and the transmission destination therein.
4

The correction value management processing section 14 starts the correction value management processing operation in response to the supply of the response time data. FIG. 2 is a flowchart showing a correction value management processing operation of the correction value management processing unit 14. The correction value management processing operation of the correction value management processing unit 14 will be described with reference to FIGS.

The correction value management processing unit 14 supplies the latest time data T 1 of the system clock 12 to the clock processing unit 1.
3 and receives the request (step 101), receives the response time data of the response data and the transmission source address thereof from the response reception processing unit 16 (step 102), and refers to the correction value management table 17. The correction value Δt corresponding to the supplied source destination is read (step 103), and (T + Δt) which is the expected time data of the local clock 24 of the source destination at the present time is calculated (step 104). Expected time data (T +
Δt) (step 105).

If T1 is equal to the expected time data (T + Δt) in the comparison result in step 105 (Y branch in step 105), it is determined that the correction value Δt is appropriate, and the correction value is not corrected and the correction value management processing is not performed. End the operation.

As a result of the comparison in step 105, T1
If it is not equal to the expected time data (T + Δt) (N branch of step 105), the current correction value is corrected according to the difference between them. In the first embodiment, the current correction value is corrected so as to eliminate the difference between them. The calculation of the new correction value is given by the following equation.

New correction value = Δt + (T 1 − (T + Δt)) / 2 The correction value management table 17 is updated with this new correction value (step 107), and the correction value management processing operation ends.

Initially, the correction value stored in the correction value management table 17 is 0 as described above, but this is corrected by the first correction value management processing operation, and almost perfect synchronization is performed in the second and subsequent synchronization processing operations. Will be taken. Note that the first correction value management processing operation is naturally performed by initial adjustment or the like, so that there is no practical problem.

As described above, in the first embodiment, the master node performs the collective maintenance management of the time correction data for the local clock and transmits and receives the time data for the time synchronization process in the normal data transmission and reception. As a result, the synchronization accuracy of the clock of the network can be significantly improved, the increase in the amount of data on the network due to the synchronization process can be suppressed, and the number of development steps can be reduced.

Factors that can be considered as fluctuations in the transmission delay time include fluctuations in traffic, changes in the route route to the transmission destination, and the like.

In the first embodiment, the corrected correction value is used at the time of the next data transmission. Therefore, the traffic and the route route change at the time when the correction value is corrected and when the corrected correction value is used. If the time fluctuates significantly,
A sudden abnormal synchronization processing operation may occur.

In the first embodiment, during the operation of the correction value management processing shown in FIG. 2, if T1 and the expected time data (T + Δt) are not equal in the comparison result in step 105 (step 1).
(N branch of 05), since the current correction value is corrected so as to eliminate the difference between the two, a sudden abnormal synchronization processing operation may occur.

Therefore, a network time synchronization system according to a second embodiment described below relaxes the sudden abnormal synchronization processing operation.

In the second embodiment, during the operation of the correction value management processing shown in FIG. 2, if T1 and the expected time data (T + Δt) are not equal in the comparison result in step 105 (step 1).
05 branch), instead of eliminating the difference between them, it is intended to compress the difference to half.

Therefore, the new correction value in step 106 of FIG. 2 is calculated by the following equation.

New correction value = Δt + (T 1 − (T + Δt)) / 4 By doing so, in the second embodiment, the convergence of the synchronization operation is normally slower than in the first embodiment, The sudden abnormal synchronization processing operation that can occur in the first embodiment can be mitigated.

As described above, in the second embodiment, the master node performs batch maintenance of the time correction data for the local clock and transmits and receives the time data for the time synchronization process to the normal data transmission and reception. As a result, the synchronization accuracy of the clock of the network can be significantly improved, the increase in the amount of data on the network due to the synchronization process can be suppressed, and the number of development steps can be reduced.

[0056]

As described above, according to the network time synchronization method of the present invention, the master node performs the batch maintenance of the local clock time correction data and transmits and receives the time data for the time synchronization processing in a normal manner. By incorporating it into data transmission / reception, it is possible to significantly improve the synchronization accuracy of the network clock, suppress the increase in the amount of data on the network due to the synchronization process, and reduce the number of development steps.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a network time synchronization method according to the present invention.

FIG. 2 is a flowchart showing an example of a correction value management processing operation in the network time synchronization method according to the first embodiment.

FIG. 3 is a block diagram showing an example of a conventional network time synchronization method.

[Explanation of symbols]

 1, 4 Time supply device 2-1 to 2-3, 5-1 to 5-3 Time synchronization device 3 Network 11, 41 Data transmission processing unit 12, 42 System clock 13, 23, 43, 55 Clock processing unit 14 Correction Value management processing unit 15, 21, 47, 51 Transmission / reception unit 16, 46 Response reception processing unit 17 Correction value management table 22, 54 Data reception processing unit 24, 57 Local clock 25, 56 Response transmission processing unit 44 Time collection processing unit 45 Time distribution processing unit 52 Time transmission processing unit 53 Time reception processing unit 101 to 107 Steps in flowchart

Claims (3)

(57) [Claims] 1. A time synchronization method for a network in which a time supply device provided in a master node and a time synchronization device provided in a plurality of nodes other than the master node are connected by a network. First time generating means for generating a reference time of the master node, time reading means for reading the time of the first time generating means, and a correction value used for generating time data for synchronization processing for each node. Correction data storage means, data transmission processing means for generating transmission data incorporating the synchronization time data at the time of data transmission, and first transmission / reception means for transmitting / receiving data to / from each of the nodes. ,
Response reception processing means for performing reception processing of reception data from each of the nodes and extracting response time data and a transmission source node address in the reception data, and corresponding to a data transmission destination node address from the correction value storage means The correction value is read out and added to the latest first reference time of the first time generation means supplied from the time reading means to create time data for synchronization processing, supplied to the data transmission processing means, and supplied to the data transmission processing means. When the correction value needs to be corrected based on the response time data supplied from the reception processing means and the latest second reference time of the first time generation means supplied from the time reading means, a new correction value is required. And a correction value management processing means for updating the correction value storage means. Second transmission / reception means for transmitting / receiving data to / from each node including a data node, data reception processing means for performing reception processing of received data and extracting the time data for synchronization processing in the received data, A second time generating means for generating a reference time, and a new time set in the second time generating means based on the synchronization processing time data supplied from the data reception processing means, and the second time generating means sets the second time in response to a request. A time setting readout unit that reads out the latest time of the time generation unit and supplies it as the response time data, and a response transmission processing unit that creates response transmission data to the master node including the supplied response time data. A time synchronization method for a network, characterized in that: 2. When correcting a correction value, a value obtained by adding one half of a difference between a second reference time and a value obtained by adding the correction value to response time data to the correction value is set as a new correction value. 2. The network time synchronization method according to claim 1, further comprising a correction value management processing unit. 3. When correcting a correction value, a value obtained by adding a quarter of a difference between a second reference time and a value obtained by adding the correction value to response time data to the correction value is set as a new correction value. 2. The network time synchronization method according to claim 1, further comprising a correction value management processing unit.