JPH03274846A - Data communication system - Google Patents

Abstract

PURPOSE:To immediately start communication without performing resetting by deciding an operating mode based on size relation between the received random number value of an opposite station and that of its own station when the operating mode of its own station coincides with that desired by the opposite station. CONSTITUTION:After the communication is started, its own station transmits an at-random value 'alpha' and the opposite station transmits an at-random value 'beta'in addition to a desired operating mode. Each station compares the size of the value 'alpha' with that of the value 'beta' when each desired operating mode coincides in 'DTE', and when it is alpha>beta, the mode of its own station goes to a DTE mode, and that of the opposite station to a DCE mode, then, the communication is started.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a communication method in which a local station and a partner station must operate in different communication operation modes. The present invention relates to a data communication system that reduces the probability of renegotiation by exchanging at-random values held by the own station during negotiation as to whether to operate in a certain mode.

[Conventional technology]

FIG. 2 is a sequence diagram showing a conventional operation mode negotiation method in data communication. In the conventional negotiation method, each station selects an operating mode (temporarily DTE (Data Ter-min)
al Equipment) operation mode, DCE (Da
ta Circuit Terminating Equ
In order to determine the mode of operation (operation mode), the local station first communicates to the other party the mode in which it would like to operate (510). As a response (520) from the other station,
There is no problem if you wish to transmit in a mode different from the mode in which your own station wants to operate, but if they are the same, after a delay due to the random timer value (T1) of your own station (D+o), your station will again switch to which mode. Send to the other party whether you would like to operate it (Sll).

If the own station receives a message requesting an operation mode from the other station during the delay due to a random timer (S21), the other station requests a different operation mode, and the operation mode is mutually determined.

A specific example is the negotiation of which station handles the oldest number search and the smallest number search of a logical channel in a dedicated line or circuit switched network that does not go through a packet network at the packet level of the x, 25 protocol. used. In the DTE mode, the oldest number search (using the largest available logical channel number) is performed, and in the DCE mode, the smallest number search is performed. This prevents both stations from using the same logical channel when attempting to call on the same logical channel at the same time.

Another prior art of this type is disclosed in Japanese Patent Laid-Open No. 1-158847. In this case, when a communication start request is received from the network layer processing device, a message from the call control processing device is used (the local station DTE/DCE mode is stored in the user-user information), and a call setup request is sent to the called communication terminal device. The state changes during the call setup process.

If a connection rejection is received from the called communication terminal during call setup processing, the DTE/DCE mode of the other station is extracted from the user information of the call control message, and the DTE/DCE modes of the own station and the other station are checked. I do. If the DTE/DCE modes of your station and the other station are the same, the DTE/DCE mode of your station
Check whether DCE mode can be changed. If the DTE/DCE mode of the own station can be changed, the DTE/DCE mode for the designated channel is changed and the call setup request is retransmitted to the called communication terminal device.

In addition, when a call setup request is received from the calling side communication terminal device, the DTE/DCE mode of the other station is extracted from the user information of the call control message, and the DTE/DCE mode of the own station and the other station is
/Check the DCE mode. DT of own station and opponent station
If the E/DCE modes are the same, check whether the DTE/DCE mode of the own station can be changed. Own station's DTE/
If the DCE mode can be changed, the local station DTE/DCE mode of the designated channel is changed, a connection request is sent to the calling side communication terminal device, the state changes to a call setup waiting state, and the call setup is performed.

[Problem to be solved by the invention]

Since the operation mode negotiation method in the conventional data communication system has the above-mentioned procedure, when both parties desire to communicate in the same operation mode, a delay for negotiation has to be added again. Therefore, there was a drawback that it took a long time until communication started.

Furthermore, the method disclosed in Japanese Patent Application Laid-open No. 1-158847 does not disclose a negotiation method when call setups that occur between stations intersect, and because the other station and the local station request call setup at the same time, they cannot call each other. When a call setup request is received in response to a setup request, if the local station and the partner station are of the same type of equipment, there is a problem that the call setup request is processed using the same algorithm and the mode cannot be determined forever.

This invention was made to solve the above-mentioned problems, and aims to provide a data communication method in which the communication operation mode is determined without renegotiation in most cases, and communication can be started more quickly. purpose.

[Means to solve the problem]

In the data communication system according to the present invention, each station has at least one
A means for setting different random values for each station in a device that has more than one type of communication operation mode, and when the own station exchanges communication data with the other station, each station performs the communication operation in a different communication operation mode from the other station. , At the start of communication, each station mutually transmits the desired communication operation mode and the set random value, and when each station has the same desired communication operation mode, it checks the magnitude relationship between the random values on the local station side and the other station side. The apparatus has means for determining a different communication operation mode for stations whose magnitude relationship is in a predetermined relationship so as to communicate in a desired communication operation, and for stations whose magnitude relationship is deviated from each other.

[Effect]

According to this invention, when the own station and the other station are in the same communication operation mode at the start of communication and request data communication, each station compares the random number value received from the other station with the random number value set by the own station, If the magnitude relationship of each random number is a predetermined relationship common to each station, that station will communicate in its own desired communication operation mode, while for other stations, the magnitude relationship will be different from the relationship set. Since communication is performed in another communication operation mode and the communication operation mode is immediately determined, it is possible to start communication immediately without negotiating again.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. As shown in the figure, after communication starts, in addition to the desired operation mode, the local station transmits an at-random value 'α', and the other station transmits an at-random value 'β'. The desired operating mode for each station is DTE'
Since they match, the magnitudes of α and β are compared and since α>β, the local station becomes DTE mode and the other station becomes DCE mode, and communication is started.

In the rare case that the at-random values match, a different at-random value is immediately set and renegotiation is performed. Although it depends on the number of digits of the atrandom value, such cases are extremely rare, and even if they occur, the mode is determined immediately because renegotiation is not performed with a delay time as in the past. The example in which the local station determines the DTE mode when α>β is the case, and the reverse may also be possible. However, in the magnitude relationship between the random values of the own station and the other station, if one is larger, it is necessary to decide whether to use DTE mode or DCE mode. If the method of determining this differs between the own station and the other station, the mode cannot be determined.

〔Effect of the invention〕

As described above, in this invention, when the desired operation modes of the own station and the other station match, the operation mode is immediately determined based on the magnitude relationship between the received random number of the other station and the random number of the own station. Communication can be started immediately without re-negotiation, and the operation mode can be determined efficiently.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a negotiation sequence according to an embodiment of the present invention, and FIG. 's2 is a diagram showing an example of a conventional negotiation sequence.

Claims (1)

[Claims] Each station has at least one type of communication operation mode,
In data communication systems, when a local station exchanges communication data with a partner station, each station performs communication operations in a different communication mode from the other station. In addition to the communication operation mode to be set, the set random value is mutually transmitted, and when each station's desired communication operation mode is the same, there is a means to check the magnitude relationship between the random values on the local station side and the other station side, and the magnitude relationship is set in advance. 1. A data communication system, characterized in that stations having a similar relationship perform communication using a desired communication operation, and stations having a different magnitude relationship have means for determining a different communication operation mode.