JPH02277337A - System for detecting station-down of called party - Google Patents

Abstract

PURPOSE:To surely detect a station-down of the called party by providing a means sending mutually to detect the station-down state of the called party and sending a command for check and a means discriminating whether or not just after the opposite station rises with the command. CONSTITUTION:An echo S command from a communicating computer A is a command to be sent for checking a station-down state of the called party when the computer A rises and an opposite station receiving the echo S command returns an echo S answer. If a computer B is in down-state during the check while the echo command is used between the computers A and B and restored, since the computer B receives the first echo just after the leading as a response to an echo R, the echo S response is returned. Thus, the restoration of the opposite station is recognized and the restart processing is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to communication between computers on a local area network, and particularly to detection of partner station down.

[Conventional technology]

Conventionally, this type of local area network does not have a function to detect when the other station is down, but can detect when the other station is down only when transmitting data.

[Problem to be solved by the invention]

The traditional local area network (LAN) mentioned above
In the above communication, since it is not possible to detect that the other party's station is down, there is a drawback that a deadlock may occur during communication or communication may not be restarted.

This will be explained using figures. In communication between computers as shown in FIG. 2, if computer B goes down at the timing shown in FIG. 3, computer A will be in a deadlock state because it cannot detect that the other station is down. Furthermore, even if you use the command to detect the partner station down as shown in Figure 3, if the sending interval of the partner station down detection command is long as shown in Figure 4(b), it will not be possible to detect the partner station down. Furthermore, if the transmission interval is shortened, the load on the LAN increases, resulting in performance degradation and line failure.

[Means to solve the problem]

The communication partner station down detection method in a local area network of the present invention includes means for transmitting =7 cloaks to mutually transmit and check each other in order to detect that the partner station is down, and when the partner station starts up in response to the command. It has a means for making it possible to determine whether it has just been done or not.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1(a) shows a partner station down detection sequence between computers during normal operation. In this figure, the communicating computer A sends an echo S command to check that the other station is down when the computer starts up, and the other station that receives the echo S command returns an echo S answer. do. After receiving the echo S answer, computer A uses the echo S answer to check whether the other station is down. The detection sequence when the other station goes down is shown in FIG. 4(b). In the figure, computer A
, 8, if computer B goes down while checking using echocommand 1~ and then recovers, echo R
Since this is the first echo reception immediately after startup, computer B returns an echo S response as a response. As a result, computer A learns of the recovery of computer B, executes the partner station down process, and executes the restart process.

〔Effect of the invention〕

As explained above, the present invention allows computers to mutually send commands to detect when the other station is down, and also provides a mechanism for determining whether the other station has just started up, thereby ensuring that the other station is down. It has the effect of detecting station towns.

[Brief explanation of drawings]

Fig. 1 shows an embodiment of the present invention, Fig. 2 shows a LAN
Figure 3 shows the communication between computers shown above, Figure 3 shows deadlock when the other station goes down, Figure 4 shows the communication between computers.
The figure shows that even if the partner station town detection command is used, there is a state in which the partner station town cannot be detected.

Claims (1)

[Claims] In a system that communicates between multiple computers using a local area network, there is a means to send commands to each other to detect when the other station is down, and to check each other, and a means for sending commands to check that the other station is up. A communication partner station down detection method, comprising means for determining whether the communication partner station has just gone up.