JPH03264890A - Timepiece synchronous apparatus in communication network - Google Patents

Abstract

PURPOSE:To take timepiece synchronism with practically sufficient accuracy even when transmission delay varies by calibrating the timepiece built in an apparatus to be controlled on the basis of the timepiece renewing start signal transmitted from a network control apparatus. CONSTITUTION:The first transmission means 3 of a network control apparatus 1 transmits a master timepiece information signal (information signal) for performing the synchronous operation of a timepiece to an arbitrary apparatus to be controlled and a time measuring means 4 starts the measurement of a time simultaneously with the transmission of the information signal and a receiving means 5 receives the master timepiece receiving response signal (response signal) from the apparatus to be controlled to stop the measurement of the means 4. The second transmission means 6 transmits a timepiece renewing start signal to an arbitrary apparatus to be controlled. The first detection means 19 of an arbitrary one of apparatuses 15-17 to be controlled detects the information signal to immediately return the response signal and an elapsed time measuring means 20 is started when the means 19 detects the information signal to measure an elapsed time. The second detection means 21 receives the timepiece renewing start signal to determine the present time from the time length data and transmission time data contained therein and the measured value of the means 20 and calibrates a timepiece 18 to make the same synchronous with a master timepiece 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a clock synchronization method within a communication network, and particularly relates to a clock synchronization method within a communication network in which the transmission delay of signals for synchronization is not constant.

[Conventional technology]

Conventional clock synchronization methods within communication networks take into account transmission delays between a network management device and multiple managed devices, and either use the transmitted time information as is or assume that the transmission delay will not change. However, the method was to add and use a fixed value as a correction value.

[Problem to be solved by the invention]

The conventional clock synchronization method within a communication network described above ignores transmission delay and sets it to zero or a constant value. There is a problem in that it is not possible to synchronize clocks with sufficient precision for practical use within a communication network where transmission delays vary greatly when traffic changes or relay routes change.

An object of the present invention is to provide a clock synchronization method within a communication network that can synchronize clocks with sufficient accuracy for practical use even within a communication network where transmission delays vary widely.

[Means to solve the problem]

A clock synchronization method in a communication network according to the present invention is a clock synchronization method in a communication network including a network management device each having a built-in clock for control and a plurality of managed devices, wherein the network management device synchronizes clocks. a first transmitting means for transmitting a master clock notification signal for performing an operation to any one managed device; a time measuring means for starting time measurement at the same time as the transmission of the master clock notification signal; receiving means for receiving a master clock reception response signal sent back from a managed device that has received the notification signal and stopping the measurement of the time measuring means; and receiving means for receiving the time length information measured by the time measuring means and the master clock notification signal. and a second transmitting means for transmitting a clock update start signal including the transmitted transmission time information to the arbitrary one managed device, and the managed device detects the master clock notification signal and immediately updates the master clock. a first detection means for returning a clock reception response signal;
elapsed time measuring means that is activated when the detecting means detects the master clock notification signal and measures the elapsed time; A second device that determines the current time based on the measured value of the elapsed time measuring means, calibrates its own built-in clock, and synchronizes it with the built-in clock of the network management device.
The configuration includes a detection means.

The clock update start signal may be transmitted only when the measured value measured by the time measuring means is less than or equal to a predetermined value.

The first transmitting means may transmit the master clock notification signal at a predetermined period.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

The network management device l includes a master clock 2 for control,
A first transmitting means 3 that transmits a master clock notification signal for synchronizing the clocks to any one managed device, and a time measuring means 4 that starts measuring time simultaneously with the transmission of the master clock notification signal. , a receiving means 5 that receives a master clock reception response signal sent back from the managed device that has received the master clock notification signal and stops the measurement of the time measuring means 4, and the time length information measured by the time measuring means 4 and the master clock. a second transmission means 6 for transmitting a clock update start signal including transmission time information at which the notification signal was transmitted to any one managed device, and connected to the relay device 8 via a transmission path 7. There is.

Relay device 8 connects transmission path 11.10 with relay device 9.10.
Connected on 12.13. The relay devices 9 and 10 are connected to each other via a transmission line 14. Each relay device 8, 9.10
are connected to managed devices 15, 16, and 17, respectively.

The managed devices 15, 16, and 17 each include a control clock 18, a first detection means 19 that detects a master clock notification signal and immediately returns a master clock reception response signal, and a control clock 18 that detects a master clock notification signal and immediately returns a master clock reception response signal. The elapsed time measuring means 20 is activated to measure the elapsed time when a clock notification signal is detected, and the current time is determined from the time length information contained therein, the transmission time information, and the measured value of the elapsed time measuring means upon receiving the clock update start signal. The network management device 1 has a built-in second detection means 21 that determines the internal clock, calibrates its own built-in clock, and synchronizes it with the master clock 2 built into the network management device 1. The master clock 2 is defined as the master clock of the clock 18, and it is required that each clock is always synchronized within a predetermined range. The synchronization signal emitted from the network management bag Kl is transmitted to the relay devices 8 and 9.
．． 10 to the managed devices 15, 16, and 17, but the transmission route in this case is not necessarily constant; for example, when transmitting to the managed device 17, the relay device 8 is directly connected to the relay device IO. It is possible to take a detour and take a route via the relay device 9.

Next, the operation will be explained. For device names and the like used in the explanation, the names and symbols shown in FIG. 1 are used.

FIG. 2 is a signal sequence diagram.

For example, in order to synchronize the clock 18 built into the managed device 17, the network management device 1 sends out a master clock notification signal S1 for synchronizing the clocks when the time of the master clock 2 is TI.

The time measuring means 4 starts measuring the time ΔT at the same time as the master clock notification signal is transmitted. It is assumed that the managed device 17 receives this master clock notification signal S1 at time 1+ of the clock 18 of the managed device 17.

The managed device 17 detects the master clock notification signal S1 with the first detection means 19, and immediately outputs the master clock reception response signal S1.
Return 2. At the same time, when the first detection means 19 detects the master clock notification signal, the elapsed time measuring means 20 is activated and measures the elapsed time Δt. The receiving means 5 of the network management device 1 receives the master clock reception response signal S2 sent back from the managed device 17, and stops the time measurement by the time measuring means 4. Next, the second transmitting means 6 transmits a clock update start signal S3 including the time ΔT measured by the time measuring means 4 and transmission time information indicating the time T at which the master clock notification signal S1 was transmitted to the managed device. Send to 17. The managed device 17 receives the clock update start signal S3 by the second detection means 21, and calculates the time T included in the signal, the transmission time information, and the measured value Δt of the elapsed time measuring means 20. The current time to is calculated and determined using the formula 1, the time of its own built-in clock is calibrated, and it is synchronized with the network management device 1 or the built-in master clock 2. True time t in this case
is within the range of TI+Δt≦t≦TI+Δt+ΔT.

t, ='rt+Δt+αΔT Equation 1 where α is the proportion of the master clock notification signal S1 during the time ΔT and takes a value of O≦α≦1.

In addition, the transmission path to which the clock synchronization method in the communication network of the present invention is applied takes into consideration that the transmission delay varies greatly, but in this case, the change in transmission delay is determined by Δt and ΔT in equation 1 appear. However, since the only problem on the managed device 17 side is the true transmission delay time of the master clock notification signal S1, the allowable error from the true time after the time of the clock 18 is calibrated is determined as the time. For example, the maximum error value of equation 1 is α
When the value of is taken as the worst value, it becomes ±ΔT. Therefore, if the network management device 1 side controls to transmit the clock update start signal S3 only when the time ΔT measured by the time measuring means 4 satisfies Equation 2, it is possible to control the clock update start signal S3 only when the time ΔT measured by the time measuring means 4 satisfies Equation 2. You can cancel the time calibration.

ΔT≦K ...Formula 2 Here, if α-172 is taken as the value of α, it is clear that the error from the true time will be within ±ΔT/2, so the numerical value can be determined in particular. Usually α-1/
Set it to 2.

In this way, α in equation 1 is α-1/2, and equation 2 is
If K is set as the allowable true time after time calibration, the error from the true time will normally be within ±/2.

Furthermore, the network management device 1 periodically synchronizes the clocks of each managed device 15, 16, and 17 to keep the time indicated by the clock of each management device in the communication network within a certain error. It becomes possible to maintain and manage the facility.

〔Effect of the invention〕

As explained above, the present invention provides a master clock reception response signal that is returned from a managed device after a network management device transmits a master clock notification signal for synchronizing clocks to any one managed device. A clock update start signal containing this time length information and transmission time information at which the master clock notification signal was sent is sent to the managed device, and based on this information, the managed device By calibrating its own built-in clock, there is the effect that clock synchronization can be achieved with sufficient accuracy for practical use even within a communication network where transmission delays vary widely.

Transmission line, 8, 9. 10... Relay device, 11, 1
2゜13.14...Transmission line, 15,16.17
...Managed device, 18...Clock, 19
......First detection means, 20...Elapsed time measuring means, Sl...Master clock notification signal, S
2... Master clock reception response signal, S3...
- Clock update start signal.

Claims (1)

[Scope of Claims] 1. In a clock synchronization method in a communication network including a network management device each having a built-in control clock and a plurality of managed devices, the network management device synchronizes the clocks. a first transmitting means for transmitting a master clock notification signal to any one managed device, a time measuring means for starting time measurement at the same time as the transmission of the master clock notification signal, and a first transmitting means for receiving the master clock notification signal. receiving means for receiving a master clock reception response signal sent back from the managed device that has received the master clock and stopping the measurement of the time measuring means; and a transmission time at which the time length information measured by the time measuring means and the master clock notification signal was transmitted. and second transmitting means for transmitting a clock update start signal including information to the arbitrary managed device, and the managed device detects the master clock notification signal and immediately transmits the master clock reception response signal. elapsed time measuring means that is activated when the first detecting means detects the master clock notification signal and measures the elapsed time; and an elapsed time measuring means that receives the clock update start signal and is included therein. a second detection means that determines the current time from the time length information, the transmission time information, and the measured value of the elapsed time measurement means, calibrates its own built-in clock, and synchronizes it with the built-in clock of the network management device; A clock synchronization method within a communication network, characterized by having the following. 2. The clock synchronization method in a communication network according to claim 1, wherein the clock update start signal is transmitted only when the measured value measured by the time measuring means is less than or equal to a predetermined value. 3. The clock synchronization system in a communication network according to claim 1, wherein the first transmitting means transmits the master clock notification signal at a predetermined period.