JPH0435244A - Inter-system time correction control system - Google Patents

Abstract

PURPOSE:To correct a time of a hardware clock accurately in a subsystem even when inter-system communication is in congestion by sending a time notice request, receiving time notice information of a main system and adding a calculated delay time to correct the time of the hardware clock. CONSTITUTION:A delay time calculation means 5 of a subsystem 3 measures a time from a transmission time t1 of a time notice request to a reception time t3 of time notice information based on the time of a hardware clock 4, uses a delay coefficient as (k), measures a time t2 of the clock of a hardware clock 2 of a main system 1, that is, t2=t3-(t3-t1)/k and obtains a delay time (a) as (t3-t2). Then a time correction means 6 adds the calculated delay time (a) to a time of time notice information from the main system 1 as a current time to correct the time of the hardware clock 4. Thus, even when the inter- system communication is in congestion, the time of the hardware clock 4 in the subsystem 3 is accurately corrected.

Description

[Detailed Description of the Invention] [Summary] Regarding an inter-system time correction control method for synchronizing the time between a main system and a subsystem, the time correction of the hard clock in the subsystem is provided even in the case of a discrepancy in communication between the systems. In an intersystem time correction control method that corrects the time of a subsystem's hard clock based on the time of a main system's hard clock, the subsystem has a delay time calculation means. and a time correction means, and the delay time calculation means calculates a sending time t1 of a time notification request from the subsystem to the main system and a time notification request from the main system based on the time of the hard clock. Information reception time t
3, the measurement time t2 of the main system is defined as t2=t3-(t3-tl
)/k, and the delay time a is determined by a=t3-tl, and the time correction means adds the delay time a to the time value indicated by the time notification information to determine the time of the hard clock. It was configured to correct.

[Industrial application field]

The present invention relates to an inter-system time correction control method for synchronizing the times between a main system and a subsystem.

It is necessary to synchronize the absolute time of the highly accurate hard clocks built into each system between systems such as a packet switch and a line switch. As a subsystem, the time of the subsystem's hard clock is corrected by the time of the main system's hard clock. In that case, if time information is to be transmitted along with other inter-system information, it is necessary to consider the transmission delay time of time information, etc.
It is desired to improve the accuracy of time correction.

[Conventional technology]

Packet switching equipment, circuit switching equipment, etc. each have a built-in highly accurate hard clock using a crystal oscillator or the like, and within the switching system, it is necessary that the absolute time of each hard clock matches.

Furthermore, various control signals between exchanges, such as between a packet exchange and a circuit exchange, are generally transmitted using a common line signaling system.

For example, if a line switch is the main system and a packet switch is the subsystem, the packet switch sends time notification requests at regular intervals to the line switch via a signal line, and the line switch uses a built-in hard clock. The time information is sent to the packet switch via the signal line, and the packet switch uses this time information to correct the time on the hard clock.

[Problem to be solved by the invention]

It is conceivable to use a line switch as the main system and a packet switch as a subsystem, and to install dedicated signal lines to match the absolute time of the built-in hard clocks of each, but this would make the signal lines more complicated. Therefore, for example, a method is adopted in which time information and the like are transmitted along with various control signals using the common line signaling method as described above.

In this common line signaling system, the protocol processing itself lacks instantaneousness, and time notification processing does not have a particularly high priority level, so for example, when the system is congested, the processing delay is extremely large. Therefore, the time value based on the received time information deviates greatly from the correct time, and therefore, there is a drawback that it is difficult to correct the time to the correct time.

In addition, in order to improve such shortcomings, the subsystem should:
It is possible to receive time information repeatedly from the main system multiple times and correct it using the reception time interval of the time information, but this increases the amount of communication and has a negative impact on the transmission of other control information, etc. This method has disadvantages, and also has the disadvantage that the amount of correction processing increases.

SUMMARY OF THE INVENTION An object of the present invention is to accurately correct the time of a hardware clock in a subsystem even in the case of interference in communication between systems.

[Means to solve the problem]

The inter-system time correction control method of the present invention calculates the delay time from the sending time of the time notification information to the receiving time of the time notification information based on the time from the sending time of the time notification request to the reception time of the time notification information, and performs time correction. This will be explained with reference to FIG.

In an intersystem time correction control method that corrects the time of a hard clock 4 of a subsystem 3 such as a packet switch based on the time of a hard clock 2 of a main system 1 such as a line switch, delay time calculation is performed in the subsystem 3. A means 5 and a time correction means 6 are provided, and the delay time calculation means 5 is a hard clock 4.
Based on the time t2, the measurement time L2 of the main system 1 is determined from the time t1 when the subsystem 3 sends the time A request to the main system 1, and the time L3 when the time notification information is received from the main system 1. =t3-(13tl)/k
Estimated by Note that k is a delay coefficient. and,
The delay time a is determined by a=t3-t2. Further, the time correction means 6 corrects the time of the hard clock 4 by adding the delay time a to the time value indicated by the time notification information.

Further, the delay time a calculated by the delay time calculation means 5 is
If the predetermined threshold is exceeded, the time notification request is sent to the main system 1 again.

[Effect]

The delay time calculation means 5 of the subsystem 3 can be realized by the calculation function of the processor of the subsystem 3, and calculates the time notification information from the sending time t1 of the time notification request based on the time of the hard clock 4. reception time L3
The time L2 at which the time of the hard clock 2 of the main system 1 is measured is estimated using the delay coefficient as k. That is, t2=t3-(t3-11)/k
Find it by In this case, it can be a value greater than 1, typically 2. Then, the delay time a is t3t
Obtained by 2.

The time correction means 6 adds the calculated delay time a to the time value in the time notification information from the main system 1 to determine the current time, and corrects the time of the hard clock 4.
It is possible to correct not only the delay caused by the signal line but also the processing delay in the main system 1. Therefore,
During normal operation, subsystem 3 is activated by periodic time notification information.
The time of the hard clock 4 can be corrected.

Furthermore, if the delay time a exceeds the threshold value, the processing delay in the main system 1 is larger than expected, so the estimation error in the measurement time t2 of the hard clock 2 of the main system 1 becomes large. Therefore, retransmission processing is performed, and the time error of the hard clock 4 of the subsystem 3 with respect to the time of the hard clock 2 of the main system 1 can be reduced.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a detailed explanatory diagram of the present invention.
), 12 is a call control processor (CPR) of the circuit exchange,
13 is a bucket switch (PPP) as a subsystem
, 14 is the main control unit (CC), 15 is the hard clock (MT
M), 16 is a main memory (MM), 17 is a channel control device (CHC), 18 is a channel adapter (CCA),
21 is the main controller (CC), 22 is the main memory (MM)
, 23 is a channel adapter (CCA), 24 is a channel control device (CHC), and 25 is a digital switching device (DS).
M), 26 is a common line controller (C3E), 31 is a main controller (CC), 32 is a hard clock (MTM), 33 is a main memory (MM), and 34 is a channel controller (CHC).
), 35 is a line control device (PLCA), and 36 is an inter-network control device (NWIF), which represent the main parts of the duplex configuration.

Various types of control information are transmitted between the common line control device 26 of the call control processor 12 and the inter-network control device 36 of the packet switch 13 using the common line signaling system. Furthermore, the arithmetic processing function of the main control device 31 of the bucket exchanger 13 as a subsystem constitutes a delay time calculation means and a time correction means, and the main control device 31 provides information such as every 30 minutes, every hour, etc. A time notification request is sent at regular time intervals, and this time notification request is sent to the channel controller 34, the line controller 35. It is sent to the signal line via the w4 control device 36, received by the common line control device 26 of the call control processor 12, and sent to the digital switching device 25 and the main control device 2.
1. Channel control device 24 Channel adapter 25 18
．． It is transferred to the main control device 14 via the channel control device 17.

The main controller 14 reads the time 11 that the time notification request was sent from the hard clock 32 and stores it, and also reads the time t3 at which the time notification information was received from the hard clock 32,
Time t2 read from the hard clock 15 of the main processor 11 is estimated using the delay coefficient k (≧1). That is, t2=t3-(t3-tl)/k---(1)
The delay time a is obtained by calculating t3-t2=a---.(2). In this case, if the time indicated by the hard clock 15 is read when the time a has elapsed from the sending time t1 of the time notification request, and the time notification information can be received at the time t3 when the time a has elapsed, the delay coefficient is is set to 2. That is, the time notification request receiving process and the time notification information sending process in the main processor 11 are executed in approximately the same time, and the transmission delay time of the time notification request and the transmission delay time of the time notification information are the same. In this case, by setting the delay coefficient k to 2, the delay time a
In other cases, the delay coefficient k is set corresponding to each time difference. It can also be determined by actual measurement.

When the delay time a is determined, the delay time a is added to the time value T indicated by the time notification information to obtain the current time, and the hard clock 3
This is to correct the time of step 2.

FIG. 3 is an explanatory diagram of the operation of one embodiment of the present invention, in which a time notification request is sent from the subsystem (packet switch 13) to the main system (line switch) at time tl indicated by the hard clock 32, and the main system Then, in accordance with the time notification request, the time T indicated by the hard clock 15 is read and sent to the subsystem as time notification information.

In the subsystem, when the time notification information is received at time t3 indicated by the hard clock 32, the hard clock 1 is
Estimate the time t2 when the time T indicated by 5 is read, calculate the delay time a using equation (2), add the delay time a to the time value T indicated by the received time notification information to obtain the current time, and set the hard clock. This is to correct the time of 32.

FIG. 4 is an explanatory diagram of the operation of another embodiment of the present invention, in which the time notification request timer TI is set to 1 hour, the retransmission timer T2 is set to 1 second, and the time notification request timer T1 sends a time notification request from the subsystem. Time t indicated by the hard clock 32
1, and sets the retransmission timer T2.

In the main system, hard clock 1 is activated by a time notification request.
The time T indicated by 5 is read and sent to the subsystem as time notification information.

The subsystem receives time notification information at time t3 indicated by the hard clock 32. In this case, if the time notification information is received within one second after sending the time notification request, the retransmission timer T2 is reset.

Furthermore, if the time notification information cannot be received within the set time (1 second) of the retransmission timer T2, the time notification request will be retransmitted.

Also, the subsystem receives time notification information and t3-t
Determine whether l≦X. χ is a predetermined threshold,
If t3-tl≦X, the delay time exceeds the threshold value X, so the hard clock 3 according to the received time notification information
Since the second time correction contains an error, the time notification request is sent again and the retransmission timer T2 is set. If the delay time for receiving time notification information due to retransmission of such a time notification request exceeds the threshold value X again, a repeated time notification request will be sent, but if the number of repetitions is set in advance and it is repeated more than the set number of times, An alarm will be sent to indicate that the time correction process has ended abnormally.

If t3-11≦X, the delay time does not exceed the threshold value X, so it is determined whether the time error ε is within the allowable range Y (ε≦Y).

This time error ε is as follows: ε=T-t2=T-(t3-a)=T-[t3-
(t3-tl)/k) -43).

If the time error ε is within the allowable range Y, 5.h-do clock 3
The time notification request timer T1 is set in order to send out the next time notification request without performing the time correction in step 2. Also, time error ε
If exceeds the allowable range Y, the delay time a is added to the time T indicated by the time notification information to determine the current time, the time of the hard clock 32 is corrected, and the time notification request timer T1 is
Set.

Let A be the processing step time required for the main system to receive a time notification request from the subsystem, and B be the processing step time required for the subsystem to receive time notification information from the main system. The delay factor is k = (A+B)/B
−(4). Moreover, the threshold value X of the delay time mentioned above is as follows:
).

Also, the accuracy P is as follows, where b is the average value of the delay time in a steady state, P≦(X/k) −b −(6)
becomes.

For example, the threshold value X [ms] is added to the delay coefficient described above.

The average value b [ms] of the delay time is k-2 and X
=500. If b=150, the precision P is P≦(50
0/2) 150=100 (ms). That is,
Main system hard clock 1 with accuracy below Looms
The time of the hard clock 32 of the subsystem can be corrected at the time of 5.

The present invention is not limited to the above-described embodiments, and various additions and changes can be made, and the main system and subsystems can be various systems including a professional sensor and a hard clock other than the exchange. It is possible.

〔Effect of the invention〕

As explained above, the present invention sends a time notification request to the main system 1 at the time L1 of the hard clock 4 of the subsystem 3, and
By the subsystem 3 receiving the time notification information indicating the time t3 of the hard clock 3, the delay coefficient is set to k,
The delay time calculation means 5 calculates the delay time a, and the time correction means 6 adds the time T based on the time notification information and the calculated delay time a to determine the current time, and corrects the time of the hard clock 4. Theoretically, there is no need to take into consideration protocol processing speed or delay time due to system comparison, and it becomes possible to correct the time of the hardware clock 4 of the subsystem 3 with high precision.

Furthermore, when the delay time exceeds a predetermined threshold for some reason, the accuracy of time correction can be improved by identifying this and retransmitting the time notification request.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is a detailed explanatory diagram of the present invention, Fig. 3 is an explanatory diagram of the operation of an embodiment of the present invention, and Fig.
The figure is an explanatory diagram of the operation of another embodiment of the present invention. 1 is a main system, 2 is a hard clock, 3 is a subsystem, 4 is a hard clock, 5 is a delay time calculation means, and 6 is a time correction means.

Claims (2)

[Claims] (1) In the inter-system time correction control method of correcting the time of the hard clock (4) of the subsystem (3) based on the time of the hard clock (2) of the main system (1), the subsystem (3) comprises a delay time calculation means (5) and a time correction means (6), and the delay time calculation means (5) comprises the hard clock (4).
Based on the time t1 when the subsystem (3) sends the time notification request to the main system (1) and the time t3 when the time notification information is received from the main system (1), the main Measurement time t of system (1)
2 and the delay coefficient is k, t2=t3-(t3-t1
)/k, and the delay time a is determined by a=t3-t1, and the time correction means (6) adds the delay time a to the time value indicated by the time notification information and adjusts the hard clock by adding the delay time a to the time value indicated by the time notification information. (4) An inter-system time correction control method characterized by correcting the time. (2) The delay time calculation means (5) causes the main system (1) to resend the time notification request when the calculated delay time a exceeds a predetermined threshold. The inter-system time correction control method according to claim 1.