JPS5840951A - Data transmitting system - Google Patents

Abstract

PURPOSE:To decrease the number of signals passing through a network and to increase the data transmission efficiency, by transmitting only the signals in the minimum required for knowing the state of terminals and at the same time eliminating the transmission through the network for the flow control signal which is repetitively used. CONSTITUTION:The data D1 is transmitted to a terminal 2 from a terminal 1, and then a signal F is sent back from the terminal 2. Thus interface devices 3 and 4 know that the terminal is unable to receive the data and store this fact. After this, the device 4 and the terminal 1 transmit the signals S'1 and S1 to the terminal 2 and the device 3 periodically or taking an opportunity of an appropriate event to inquire whether the terminal 2 is able to receive the data. Thus the terminal 2 and the device 3 transmit the signals R'1 and R1 in reply to show the incapability of reception. A signal Q showing a receivable state is given from the terminal 2 and then fed to the device 3 by the device 4 via a network 5. The device 3 delivers the signal Q showing a receivable state in reply to the inquiring signal Sn sent from the terminal 1. Then the normal data is transferred between the terminals 1 and 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data transmission system, and more specifically, flow control when data terminals communicate with each other or between a data terminal and a computer via a network having a store-and-forward function such as a network exchange network. A data and evening communication network consisting of a network with a store-and-forward function, an interface device for connecting data terminals and matching the interface with the network, or a computer terminal directly connected to the network. In general, when receiving or transmitting data becomes temporarily impossible at the own terminal or the other party's terminal, a method is adopted in which specific signals are repeatedly transmitted and received between the two until the cause is removed. This is called flow control.

Flow control signals include, when a data receiving terminal is temporarily unable to send data, a signal issued by the data receiving terminal indicating that reception is temporarily disabled, and a signal issued by the data transmitting terminal indicating whether reception is possible. and, when a terminal transmitting data is temporarily unable to transmit, a signal issued by the data transmitting terminal indicating that transmission is temporarily unavailable, and a signal issued by the data receiving terminal acknowledging that transmission is not possible. There is.

By the way, in conventional data communications, all signals, including the above-mentioned flow control signal, which is repeated as long as the flow control factor continues, are directly transmitted to the other party's terminal through the network. The number of data transfers increases, which reduces the data transfer efficiency of the network.

In order to eliminate these drawbacks, the present invention transmits the first flow control signal sent from a data terminal or computer terminal to the other terminal through the network, but the flow control signals that are repeated thereafter are processed by the interface device. The data is not transmitted through the network, and only when the flow control factor is removed is the data transmitted to the other party's terminal (2) through the network.The drawings will be described in detail below.

The figure shows an embodiment in which the present invention is applied to data reception. In the figure, 1 is terminal A, 2 is terminal B, 3
4 is an interface device A of terminal 1, 4 is an interface device B of terminal 2, and 5 is a network having a store-and-forward function.

Dl and D2 are data. F is a flow control signal indicating that reception is temporarily disabled, which is returned by the terminal 2 when receiving the data D1.

Sl, S2. ..., Sn is a signal for terminal 1 to inform terminal 2 whether or not the unreceivable state has been released;
""1 r S'2, ~S'□ is the interface device 4
is a signal to terminal 2, replacing terminal 1, to interrupt the unreceivable state, and ■1 to Rn-1 is a signal from which the interface device 3 replaces terminal 2 and sends a signal to terminal 1, indicating that the unreceivable state is still continuing. R'1 to I't'm -1 are signals indicating that the terminal 2 is not yet able to receive data, Q is a signal indicating that the terminal 2 is ready to receive data, and D2 is a signal that indicates that the terminal 2 is not ready for reception. This is the first data sent after the disabled state is released.

Now, after data DI is transmitted from terminal 1 to terminal 2, when signal F is returned from terminal 2, interface device 3
, 4 learns that terminal 2 is in a non-receivable state and stores this information. Thereafter, the interface device 4 transmits the signal B11 to the terminal 2 periodically or triggered by other appropriate events.
It is then determined whether terminal 2 is ready for reception. For this ζ=, terminal 2 sends signal R/1,
If reception is not possible, the signal S2 is triggered in the same way as above.
send.

This is repeated until the terminal 2 returns the receivable signal Q.

On the other hand, if the terminal 1 sends the signal S1 to return the signal F and the state of the terminal 2 is adjusted, the interface device 3 returns the signal R1 to the terminal 2 (instead, returns the signal R1 to the terminal 1, Informs the terminal 2 that it is still unable to receive data.This process is repeated until the signal Q indicating the receivable state sent from the terminal 2 reaches the interface device 3 via the interface device 4.The signal Q is sent from the terminal 2. When the signal Q is received from the terminal 2, the interface device 4 sends the signal Q to the interface device 3 via the network 5. When the signal Q from the terminal 2 arrives, the interface device 4 can receive the signal Q from the terminal 1. Terminals 1 and 2 then start normal data transfer between terminals 1 and 2.

That is, between the signal F indicating unreceivable to the signal Q indicating receivable (2. Signals 81 to Sn and R'1 to *m-1 transmitted from terminal 1.2 are transmitted within the network 5. There isn't.

Although the figure relates to reception (==reception), it can be similarly applied to flow control signals related to transmission.

Furthermore, regarding communication between a computer terminal directly accommodated in a network and a terminal connected to an interface device, it is sufficient to consider that the computer terminal is located at the location of the other party's interface device.

As explained above, according to the present invention, only the minimum necessary signals to know the status of a terminal are transmitted within the network, and the transmission of repeatedly used flow control signals within the network can be omitted. This reduces the number of signals passing through, increasing the data transmission efficiency of the network.

[Brief explanation of the drawing]

The figure is a diagram for explaining one embodiment of the present invention. 1.2...Terminal, 3.4...Interface device, 5...Network, DI+-D2"' data, 8l-sn, s."s'm...State adjustment signal , F... Temporary reception unavailable signal, 几1~Rn -1+ R'1~'''m -
1"' Reception temporarily unavailable signal, Q...Receivable signal. Agent: Patent attorney Makoto Suzuki 1. "Continued from page 1 ■Applicant: Hitachi, Ltd. 5-1 Marunouchi-chome, Chiyoda-ku, Tokyo 1-7-12 Toranomon, Minato-ku, Tokyo Stop @Applicant Fujitsu Ltd. 1015 Kamiodanaka, Nakahara-ku, Kawasaki City

Claims (1)

[Claims] 1. A data communication network consisting of a network with a store-and-forward function, and an interface device for connecting data terminals and matching the interface with the network, or computer terminals directly connected to the network: 2. When reception or transmission is temporarily disabled, the first flow control signal sent from the data terminal or computer terminal is transmitted to the other party's terminal (2) through the network, and thereafter the flow control signal (2) is transmitted repeatedly as long as the flow control factor continues. Second, when a signal indicating cancellation of the flow control factor is transmitted by processing between the interface device and the corresponding terminal and preventing transmission within the network,
A data transmission method characterized by transmitting the signal to the other party's terminal through a network.