JPH04235433A - Cyclic polling system - Google Patents

Abstract

PURPOSE:To level the throughput between respective workstations. CONSTITUTION:Plural workstations serve to mutually transmit/receive data via a transmission line 15. The respective workstations consist of a receiving control part 16 conducting the receiving control, a transmission control part 17 conducting the transmission control, a receiving data queue 18 storing the receiving data, a transmission data queue 19 storing the transmission data and a CPU20 conducting the control of these parts. The respective workstations judge current average data length, judge what times the length of data to be transmitted is the average data length, and when the length of the data to be transmitted is once or less than the average data length, immediately transmit the data while responding to a polling, or when the length of the data to be transmitted is once or more than the average data length, pass up the polling by the number of times equivalent to a multiple of the average data length.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD The present invention relates to a circular polling system.
More particularly, the present invention relates to a single-restriction cyclic polling system that transmits frame-by-frame data having arbitrary length data between stations by sequentially passing transmission rights between a plurality of workstations.

0002

[Prior Art] In this type of conventional single-limit circular polling system, the bandwidth used by each workstation is dynamically changed according to the system throughput of the entire network to level out the throughput among each workstation. The disadvantage is that it cannot be done.

0003

OBJECTS OF THE INVENTION The present invention has been made to solve the drawbacks of the prior art, and its purpose is to provide a cyclic polling system that makes it possible to equalize the throughput between workstations. It is about providing.

0004

SUMMARY OF THE INVENTION According to the present invention, there is provided a single-restriction cyclic polling system for transmitting data one frame at a time having data of arbitrary length between stations by sequentially passing transmission rights among a plurality of workstations. And,
A means for calculating the data length to be transmitted, a means for calculating a polling cycle by observing the cycle of polling indicating transmission rights, and a means for calculating the current polling cycle based on the data length, the polling cycle, the line speed, and the number of stations. means for determining whether frames with a data length of A cyclic polling system is obtained, which is characterized in that each workstation is provided with the following.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, referring to FIG. 2, a schematic configuration of a system to which the present invention is applied is shown. The plurality of workstations 11 to 14 have a function of mutually transmitting and receiving data via a transmission line 15.

FIG. 3 is a block diagram inside each workstation. A reception control unit 16 that performs reception control, a transmission control unit 17 that performs transmission control, a reception data queue 18 that stores reception data, a transmission data queue 19 that stores transmission data, and a CPU 20 that controls each of these parts. The configuration includes

[0008] The frames sent out on the transmission path 15 are taken into the device by the reception control section 16 at the destination station and accumulated in the reception data queue 18. The data to be transmitted accumulated in the transmission data queue 19 is sent to the transmission path 15 via the transmission control unit 17 in frame units of arbitrary data length.
sent to. The transmission operation control of this transmission control section 17 is
This is performed by the PU20.

When each workstation mutually transmits data of arbitrary length, if the amount of data that one station can transmit per unit time is defined as the throughput of each station, then the variation in this throughput between stations can be equalized. become

By receiving polling, which is a transmission right, each station has the right to send data as a frame to a transmission path. Let M be the data length of each frame.

[0011] The number of stations in the network and the line speed are known (constants) once the system is determined, and the traffic on the network can be calculated by dividing the average polling cycle by the number of stations. Defined as the average data transmission time. Note that if the overhead for polling cannot be ignored, it is necessary to take this overhead α into consideration in advance.

Therefore, from the opposite perspective, the polling cycle time T for any data length can be determined from the number of stations in the network and the line speed, and this T is T={
(Data length) ÷ (Line speed)} × (Number of stations) +
α...It is expressed as (1).

[0013] This polling circulation time T can be calculated by measuring it with a timer during actual operation, so (1)
The data length of the equation, that is, the average data transmission time per station (equivalent to the average data length) can be found.

[0014] Therefore, if a correspondence table between the average data length N and the polling circulation time T is provided using the number of stations and the line speed as parameters, N at T during actual operation can be determined.

[0015] In order to stabilize network traffic, it is sufficient for each station to send data with an average length close to N per polling.
When transmitting a large frame with data length M, M/
It is sufficient to wait for polling N=P times before transmitting.

[0016] The value of N can be stabilized by taking the average of several times and updating it with that value. The station operates according to the following rules:

(1) When the length M of the data at the head of the transmission data queue is less than or equal to N, the frame is transmitted immediately after being polled.

(2) When the length M of the data at the head of the transmission data queue is P times N, the frame is transmitted after waiting until the P-th polling (polling in the meantime is postponed).

[0019] If each station performs the transmission operation in this manner, the throughput among the stations will be equalized. Therefore, the CPU 1 performs the operation processing shown in FIG.

When the data to be transmitted is accumulated in the transmission data queue in step 1, the transmission data length M is calculated (detected) in the next step 2. At the same time, a polling period T is calculated in step 3, and this polling period is calculated by measuring it using a timer at any time.

In step 4, the average data length N is determined based on the calculated polling period T. This determination of N is performed by referring to the average data length table 5. That is, as described above, using the number of stations and the line speed as parameters, the average data length N obtained corresponding to each polling cycle time T is calculated in advance according to formula (1), and the correspondence table 5 is obtained. N is determined by providing it to the CPU of each station.

[0022] Then, in step 6, from N, M to P=
M/N is calculated, and in step 7 it is determined how many times the transmission data length is the average data length.

If P is less than 1, then in step 9 the transmission data in the transmission data queue is sent out in response to polling. If P is greater than 1, polling is postponed until P becomes less than 1 (step 8).

[0024] In this case, P is limited in advance to within a certain value depending on the buffer capacity in the device, etc., but in addition to this, a restriction is added such that P is truncated to within a certain value (system parameter). is also good.

[0025]

As described above, according to the present invention, the current average data length is determined, and the data length to be transmitted is determined how many times the average data length is. If there is, data is immediately transmitted in response to polling, and if it is greater than 1, polling is postponed a number of times corresponding to the multiple, which has the effect of leveling the throughput between each station.

[Brief explanation of the drawing]

FIG. 1 is a processing flow diagram showing the operation of an embodiment of the present invention.

FIG. 2 is a schematic system block diagram of a cyclic polling system to which the present invention is applied.

FIG. 3 is a block diagram showing the configuration of each workstation.

[Explanation of symbols]

11-14 Workstation 15 Transmission line 20 CPU

Claims (1)

[Claims] Claim 1: A single-restriction cyclic polling system for transmitting data one frame at a time having data of arbitrary length between stations by sequentially passing transmission rights among a plurality of workstations, the system comprising: means for calculating the data length to be used; means for calculating the polling cycle by observing the cycle of polling indicating transmission rights; means for determining whether or not frames of the data length are flowing on average; and means for determining whether or not transmission is possible after how many polls are performed based on the ratio of the data length to be transmitted to the determined average data length. , a cyclic polling system characterized by being installed at each workstation.