JPH0365702B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a network control system in a local area network, and particularly to a network control system that enables multiple communication control in a token passing system.

In recent years, with the rise of office automation, so-called local area networks (LANs), in which multiple office devices are connected via inexpensive and simple commercial network transmission lines, have been actively developed. In this type of local area network, a large number of terminal stations are generally branch-connected to a single common network transmission path, and communication between the terminal stations is performed via the shared transmission path. Therefore, 2
If transmission is started from two or more terminal stations at the same time, there is a risk that communication signals will be disrupted, or so-called communication collisions will occur. Therefore, in order to avoid this "communication collision," several control methods have been proposed to adjust the transmission start timings of all stations in the network.

Among them, token passing (TOKEN
The PASSING method is known as one of the superior methods, but this method sets a communication right that allows the network transmission path to be used exclusively, and the When the transmitting terminal station that has acquired communication rights ends communication, or when there is no need to communicate from the beginning, this communication right is transferred to another terminal station. It is based on the principle of handing over things. Furthermore, in this method, in order to give each station in the network an equal opportunity to communicate, each station that has finished communicating passes the communication rights to the adjacent downstream station one after another, and the communication rights are transferred within the network. A so-called cyclical GO AHEAD format is commonly employed. Note that this type of communication control is generally achieved using firmware (microprogram).
For this reason, each station in the network is usually equipped with a small processor. Further, each station in the network usually always recognizes at least the address of the downstream station to which it should next transfer communication rights, by polling or some other method. In this way, in token passing data communication,
Since there is only one station in the network that makes calls at the same time, the above-mentioned "communication collision" cannot occur.

However, in such a conventional token passing system, it is not possible to perform multiplex communication even when there are transmitting stations that have idle intervals during communication operations. In other words, because the number of stations connected to a local area network transmission line often changes depending on the user's system configuration, communication rights once relinquished are returned to the original station after circulating through all other stations. There was no guarantee of time for return to the station. Therefore, it is difficult to perform multiplex communication using the conventional token passing method. could not be transferred to another station. However, it often happens that a station that has obtained communication rights temporarily suspends communication operations because office equipment under the station performs mechanical operations such as printing. However, even at that time, the communication right could not be passed to the next downstream station, and the communication operation of the entire network was temporarily stopped, resulting in a problem that the communication efficiency was significantly reduced.

An object of the present invention is to eliminate the above-mentioned drawbacks and improve the communication rights delegation method of the go-ahead type token passing method, so that when a predetermined station is communicating,
When idle time occurs, a method is provided to temporarily transfer communication rights to another station and allow the original station to regain communication rights even if the communication rights do not go around the network, thereby reducing multiplex communication processing. The object of the present invention is to provide a network control method that enables operation.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows an example of the structure (format) of communication data used in the network control system of the present invention.
Similar to HDLC (High Level Data Link Control Procedure) communication, here 1 is the first flag area indicating the beginning of the (transmission) data, 2 is the receiving station address area where the address of the destination station or downstream station is written, and 3 is the receiving station address area. A transmitting station address area is used to write the address of the source station, and 4 is a data/control data area where either (transmission) data or control data is written.
Further, 5 is an FCS area for checking the validity of received data, and 6 is a second flag area indicating the end of transmitted data.

Complete delegation of communication rights to another station by token passing in this example is performed using control communication data as shown in FIG. 1, and this communication data is hereinafter referred to as a TOKEN (token) command.
After receiving this TOKEN command, the station will be able to transmit communication data on its own. The remaining stations can only receive these communication data and transmit their response data.

Furthermore, as mentioned above, the receiving station that has received the temporary communication rights transfer command receives an acknowledgment (hereinafter referred to as ACK) or a rejection response (hereinafter referred to as NACK) from the original transmitting station after completing the specified data transmission. The ACK or NACK response is written into the control data area 4, for example.

Figures 2 and 3 are the same as Figure 1, respectively.
The figure schematically shows how the TOKEN command propagates on the network according to the present invention, where a is the network transmission path, b to g are communication data transmitting/receiving stations, and the arrows in the figure are the TOKEN commands. shows the direction of propagation. In this way, in this example, the transmission path is assumed to be unidirectional and ring-shaped. FIG. 4 is a flowchart showing an example of control operations for input data of each station in this embodiment shown in FIGS. 2 and 3. FIG. Next, the control operation of this embodiment will be explained with reference to FIGS. 2 and 3 with reference to FIG. 4.

First, FIG. 2 shows a network control operation similar to the conventional token passing method, but in this example, this operation is performed when no multiplexing operation is performed, that is, when there is no communication request at each station, TOKEN
This corresponds only to the case where the communication operation is completely completed at the station that received the command and the communication right is sequentially handed over to the next station (steps S1 to S4). On the other hand, when it is necessary to start multiplex operations at a station that has obtained communication rights using the TOKEN command (steps S5 and S6), the TOKEN command is used as shown in Figure 3.
The way commands are circulated changes.

Here, it is assumed that the station d in FIG. 3 requires multiple operations, and that one communication operation includes waiting processing due to mechanical operations or other causes. After obtaining communication rights (step S1), starting communication operation (step S2), and proceeding to the waiting process (step S5),
Station d once sends a TOKEN command to the next station e (step S6) and relinquishes communication rights, but this TOKEN command data has a flag bit set in a certain control data area 4, or a command in control data area 4. The code itself is changed to clearly indicate that this is a temporary transfer of communication rights. This temporary communication rights transfer order will be applied to EXPRESS from now on.
It is called TOKEN (Express Token) instruction.
This will be distinguished from the normal TOKEN command.

Next, station e, which received the EXPRESS TOKEN command, has been delegated communication rights, even if only temporarily (step S21), so it can make calls to process data communication requests accumulated within its own station. Become. however,
Of these data communication requests, station e selects and processes only those that will complete the communication process in as short a time as possible, so as not to occupy the network for a long time (steps S22 and
S23).

When the short-term communication ends (step S24), station e first returns an EXPRESS TOKEN command to station d, which is the station that originally sent the EXPRESS TOKEN command, and attempts to return the communication right (step S25).

If the waiting process has already been completed at station d (step S8), the delegation command is accepted, a positive ACK response is sent from station d to station e (step S10), and the communication right is returned to station d. (Step S26).
If station d is still in the waiting process, it rejects the transfer command as it is not yet time for data communication, and returns a rejection NACK response from station d to station e (step S8).
and step S9). At this time, station e determines that it was unable to return communication rights to station d (step S26), and furthermore, since station d's waiting process is still continuing, it uses this time to transfer communications to other stations. EXPRESS TOKEN to station f, the next downstream station, so that it can be used effectively.
Issue a command (step S28). The important thing to note here is that it is issued for station f.
This means that the transmitting station address of the EXPRESS TOKEN command is not station e, but remains the address of station d, which is the original hyperactive node (NODE). Therefore, station f is directly connected to station d.
It will appear as if an EXPRESS TOKEN command has been sent.

Station f, like the operation of station e described above, performs a short communication process (steps S1, S21 to S24), and then sends EXPRESS to the original sending station d of the EXPRESS TOKEN command.
Attempts to re-delegate communication rights using the TOKEN command (step S25), and the response from step d is an affirmative ACK.
If it is a response, it returns to the initial state and returns to the negative state again.
If it is a NACK response, an EXPRESS TOKEN command is sent to the next downstream station g (steps S26 to S28). At this time, the sender address of the EXPRESS TOKEN command issued to station g is kept at the address of station d, which is the original multi-operation node, as in the case of the station described above. In this way,
EXPRESS returned to station d
As long as the TOKEN command is rejected with a negative NACK,
The EXPRESS TOKEN command is sequentially passed to downstream stations, and the waiting time of station d continues to be effectively used for communication processing of other stations.

Now, because the waiting time at station d was long, the call was made from station d first.
Assuming that the EXPRESS TOKEN command goes around the network and reaches station c, which is the upstream station immediately before station d, and the communication process at station c ends, station c at this time will always be connected to one of the stations. It is necessary to delegate communication rights. Otherwise, network communication will be interrupted.
Therefore, station c must delegate communication rights to station d.

For this reason, each station is required to perform yet another judgment process. That is,
Each station that has completed the specified data communication in response to the EXPRESS TOKEN command must compare the original multi-operation station address with its own downstream station address before issuing the EXPRESS TOKEN command to the downstream station (step S28). (Step S27), if they match, the above-mentioned EXXPRESS TOKEN command is sent (Step S28), but if the two addresses match, the EXPRESS TOKEN command is sent.
This is changed into a TOKEN command and returned to the original multi-operation station (step S29).

Here, since all stations are controlled to always accept the TOKEN command even during multiprocessing operation (step S1), station c sends the TOKEN command to station d, and station d receives this command. will definitely be accepted. At this time, if the waiting process has been completed at station d, data communication will be resumed (step S2), but if the waiting process has not yet been completed, the EXPRESS TOKEN command will be sent to station e again (step S2). In step S6), the process proceeds to the same operation as described above. When station d completes communication processing (step S3), the TOKEN command is passed to station e for the first time (step S4), and the second
The state returns to the normal communication rights transfer state as shown in the figure.

Note that in this example in Figures 2 and 3, a network transmission path on a ring is assumed, but if the communication rights delegation command logically circulates equally among all stations in the network, it is possible to The present invention is applicable regardless of the shape of the network transmission path.

Also, in this example, a TOKEN command is sent from station c to station d, but
If there is a configuration in which all stations in the network memorize the upstream and downstream relationships of all stations in advance, then when station c issues an EXPRESS TOKEN command to station d and then returns a NACK response, the station Jump over d and directly EXPRESS from station c to the next station e.
It is also preferable to issue a TOKEN command.

As explained above, according to the present invention, when a station that generates idle time during one communication process is included in a token passing type local area network, the idle time is used for communication processing at other stations. By making it available, it is possible to improve the communication efficiency of the network.

Furthermore, since the present invention has a simple configuration, it can be easily achieved by simply making predetermined changes to the communication control firmware of each station, and has the advantage that it can be realized at a relatively low cost.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the structure of communication data used in the present invention, FIGS. 2 and 3 are state diagrams showing an example of the flow of communication data during communication to which the present invention is applied, and FIG. is a flowchart showing an example of the control operation of each station in FIGS. 2 and 3. FIG. a...Network transmission line, b, c, d, e,
f, g...Communication data transmission/reception station, 1...
First flag area, 2... Receiving station address area, 3...
Transmitting station address area, 4...Data/control data area, 5...FCS area, 6...Second flag area.

Claims (1)

[Scope of Claims] 1. In a token-passing type network in which only a station that has obtained communication rights can perform data communication independently, the station communicates with the transmitting station and the receiving station when there is idle communication time during the data communication. communication right temporary transfer means for temporarily transferring the communication right to another station via a communication right temporary transfer instruction including an address of the station; A network control system characterized by comprising communication rights re-taking means for allowing a station to regain the communication rights again. 2. In the network control system as set forth in claim 1, the other station that has received the communication rights temporary transfer command is the sender of the communication rights temporary transfer command after completing its own data communication processing or when data communication is not required. A network control system characterized by comprising communication right return means for returning the communication right temporary transfer command to the station. 3. In the network control system according to claim 1 or 2, the communication right reacquisition means sends a refusal response to the other station to the effect that the station is in the process of waiting, or completes the process of waiting. The network control system further comprises means for transmitting an acknowledgment to the effect that the communication rights have been temporarily transferred, and the other station receiving the rejection response further comprises means for transferring the communication right temporary transfer command to a downstream station. 4. The network control system according to claim 3, characterized in that the transmission station address of the communication right temporary transfer command transmitted to the downstream station is the address of the station that first transmitted the command. network control method.