JPH1198167A - Transmission flow control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the transmission flow control method in which a transmission error rate and a load on a transmission channel are reduced. SOLUTION: Each of computers A, B, C adds its own load state information to a free token FT when each receives the free token FT and conducts regenerating relay by utilizing a principle that the free token FT is circulated through the computers A, B, C in a token ring LAN. The computer B going to send data obtains a data amount that is received by the computer A being a data transmission destination from the load state information upon the receipt of the free token FT, changes the free token FT into a busy token BT and sends data within the data amount permitted by the load state information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission flow control method for connecting a plurality of computers via a loop transmission path and transmitting data to each other, and more particularly to a transmission flow control method using a free token in a token ring type LAN. About.

[0002]

2. Description of the Related Art As shown in FIG.
Are connected by a loop transmission path 4 and transmission flow control for data transmission between computers employs a method of adding flow control information to a response signal according to a load state of a data receiving side and notifying a transmission source computer of the response signal. Thus, congestion of transmission data and the like are eliminated.

For example, in transmitting data from the computer 1 to the computer 2, as shown in FIG. 3, data is transmitted from the transmitting computer 1 to the receiving computer 2, and the receiving computer 2 responds to the response signal. AC
K is returned to the transmitting computer 1. This response signal A
The CK contains information on the amount of data that can be received next time or information on the delay time until the next data is transmitted. The transmitting computer 1 that has received this information adjusts the data amount or the delay time for the next transmission and transmits the data.

[0004]

The conventional transmission flow control has the following problems.

(1) The transmission source computer cannot acquire the load state information of the partner computer unless the first data has been transmitted.

(2) The load state of each computer can be recognized only by the computer that transmitted the data.

[0007] From these matters, when the load on the receiving computer is high, the transmission error rate increases, and the transmission path load also increases due to data retransmission and the like.

For example, in the configuration shown in FIG. 2, the computer 2 transmits a data amount x to the computer 1, and upon receipt of the data, the computer 1 returns the next data reception allowable amount n ₁ to the computer 2. 3 transmits the data amount n ₂ (> n ₁ ) to the computer 1, the computer 1 cannot receive the data amount n ₂ ,
The communication error is returned to the computer 3, and the transmission error rate increases. In addition, since the computer 3 retransmits the data in response to the communication error, the transmission path load increases.

An object of the present invention is to provide a transmission flow control method capable of reducing a transmission error rate and a transmission path load.

[0010]

The present invention utilizes the fact that a free token circulates around each computer in a token ring type LAN (local area network), and uses this free token to store the load status information of each computer. In addition, the information is reproduced and relayed, and the computers obtain the mutual load state from this information to reduce the transmission error rate and the transmission path load. The method is characterized by the following method.

A plurality of computers are token ring type L
In a system in which each computer transmits data to each other via an AN, when each computer receives a free token circulating through a LAN transmission path, each computer adds its own load status information and reproduces and relays the information. Out of which, when receiving the free token, the computer that seeks to transmit the data obtains the amount of data that can be received by the data transmission destination computer from the load state information, and transmits the data within the range of the data amount. It is characterized by.

[0012]

FIG. 1 shows a transmission flow control procedure according to an embodiment of the present invention. FIG. 7A shows a state in which a free token circulates between the computers A, B, and C. The token includes a free token (FT) when the transmission path is empty and a busy token (B) when the transmission path is in use.
It is circulated in the network with the indication of T).

Each of the computers A, B and C reproduces and relays the free token to the next computer if there is no transmission data when the free token is received. Then, the computer transmitting the data obtains the transmission right when receiving the free token, changes this token to a busy token that designates the destination computer, attaches the token to the head of the transmission data, and adds the token to the transmission path. Put on.

The busy token and the data are sequentially reproduced and relayed by each computer, and when the computer arrives at the transmission destination computer, the busy token and the data are taken in by the computer, and the data is displayed and received again. The busy token that has returned to the source computer after making one round of the ring is returned to the free token and transmitted again.

In this embodiment, load state information of each computer is added to the tour of the free token (FT) so that each computer can acquire this information. In FIG. 1A, when the computer A sends a free token, its own load state information A is added to the free token FT. The computer C that has received this information acquires the load state information A of the computer A, adds the load state information C of itself to the free token FT, and transmits the free token FT. Similarly, the computer B acquires the load state information of the computers A and B, adds the load state information B of the computer B, and sends it out.

All the computers A, B, and C on the network have acquired the latest load state information of the other computers by circulating the free token to which the load state information is added, and will transmit the data. Transmits the data within a range that does not cause a transmission / reception error according to the load state information of the transmission destination computer.

FIG. 1B shows a case where data is transmitted from the computer B to the computer A. When the computer B receives the free token, the computer B obtains the load state information of the computers A and C added thereto, calculates the amount of data allowed to be transmitted based on the load state information of the computer A, and converts the free token into a busy token. And the computer A is specified as the data transmission destination, transmission data is added to this data, and the transmission is made to the transmission path. Computer A receives the busy token and the subsequent data when the destination matches.

Therefore, each computer can recognize the load state of the destination computer prior to data transmission, and can transmit the data with an appropriate data amount without causing a transmission / reception error from the first data transmission. Further, since load state information can be obtained without depending on the data transmission amount and the data transmission frequency, the overhead of the transmission protocol is not increased.

[0019]

As described above, according to the present invention, the load status information of each computer is added to the free token circulating on the transmission path of the token ring type LAN, and the computers obtain the mutual load status from this information. Since the transmission is performed with an appropriate amount of data, each computer can perform data transmission by acquiring the load state of the destination computer before data transmission, and can reduce the transmission error rate and the transmission path load.

Further, a special protocol for acquiring the load state information is not required, and the overhead of the transmission protocol is reduced.

[Brief description of the drawings]

FIG. 1 is a transmission flow control procedure according to an embodiment of the present invention.

FIG. 2 is an example of a system configuration for performing transmission flow control.

FIG. 3 is a conventional transmission flow.

[Explanation of symbols]

 1-3, A-C: Computer 4: LAN FT: Free token BT: Busy token

Claims (1)

[Claims] In a system in which a plurality of computers are connected by a token ring type LAN and each computer transmits data to each other, each computer receives a free token circulating through a transmission path of the LAN, and each computer receives its own load state. The information is added and the information is reproduced and relayed, and among the computers, the computer that intends to transmit data obtains the amount of data that can be received by the data transmission destination computer from the load state information when the free token is received, A transmission flow control method characterized by transmitting data within this data amount range.