JPH04132433A - Communication control system - Google Patents

Abstract

PURPOSE:To improve the communication quality of a multiple address data frame by sending a reply frame to a transmission station when information representing a transmission station address in the multiple address data frame is coincident with preceding station address information provided in its own station upon the receipt of the multiple address data frame. CONSTITUTION:When the token passing bus access system is in use and a multiple address data frame 7 is received, and when information representing a transmission station address 10 in the data frame 7 is coincident with preceding station address information provided in its own station, a reply frame is sent to a station sending the multiple address data frame 7. When they are dissident, it is confirmed that an reply frame to the data frame coincident with the preceding station address information provided in its own station is sent from the preceding station, and the reply frame is sent to the station sending the multiple address data frame 7. Since the acknowledge frame from each station is sequentially received to the multiple address data frame 7, the quality of the transmission frame is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a communication control method in a local area network, and particularly relates to a communication control method for transmitting a response frame to a simultaneous broadcast communication using a token passing bus access method. .

[Conventional technology]

Traditionally, such local area networks (hereinafter referred to as LA
There is a protocol called a token-passing bus access method. This method is based on the ISO standard, which was approved as an international standard in 1987.
8802-4C Information Processing
System Boot LAN - Part 4 Token Passing Bus Access Methods and Physical Layer Specifications].

This token passing bus access method is
It is located at the lower layer of the N protocol. Moreover, this method is one of the protocols for receiving information frames on a communication medium, and if it is a data frame addressed to the current station, reporting the received information to the upper layer or controlling access to the communication medium. It is.

Access control to communication media is performed using a token system, and this token is a control frame that controls communication media access rights, and the station that holds this token obtains the right to transmit data frames. Furthermore, communication between each station is performed by receiving and passing tokens from one station to another.

Also, the physical form of the communication medium is bus-type, and stations on the network always receive frames transmitted on the communication medium.

Each station on the network described above has three address information: the preceding station address, the own station address, and the succeeding station address.
This logically constitutes a ring-shaped network. In this logical ring, each station receives and receives a token frame from the preceding station, transmits the data frame to be transmitted, and after transmission is completed, passes the token frame to the succeeding station.

By the way, the frame has a control field, a destination address,
field, source address field, and the control field within this field determines whether the frame is a token frame or a data frame. The destination address field indicates the destination of the frame, and is usually set to the address of one station on the network. Further, the address of the transmitting station is set in the source address field. The receiving side uses this information to determine whether the received frame is addressed to the current station.

Typically, data frames are sent to one station on the network. Then, the station that received the data frame transmits a response frame in response. This response frame is transmitted when the receiving station receives a token frame addressed to itself and obtains the right to transmit. In addition, the data frame includes an immediate response request data frame, and when a data frame is transmitted in this format, the receiving station can immediately transmit a response frame on the spot even if it does not have a token frame. can.

Furthermore, in the case of an immediate response request data frame, the transmitting station also expects that a response frame will be sent after transmission.
Receive frames on a communication medium.

In this way, in the case of one-to-one transmission and reception of data frames, by returning a response frame, it is possible to confirm whether the data has been correctly transmitted to the other station.

On the other hand, data frames have one more pair of transmissions and receptions, and a simultaneous broadcast data frame corresponds to this. This broadcast data frame is sent to all stations on the network and is constructed by setting the destination address to a specific value (usually a value in which all bits in the destination address field are set to 1).

Even if this simultaneous broadcast data frame is received, the receiving station does not transmit a response frame.

Therefore, the transmitting station cannot confirm whether or not the data has been correctly received only for this frame. Moreover, for this reason, even if the data is not transmitted correctly, the simultaneous broadcast data frame can only send information that has little effect on the receiving station or on the management and maintenance of the network. In the case of an immediate response request frame that requires a response frame for each frame, it cannot be transmitted as a broadcast data frame.

[Problem to be solved by the invention]

In the conventional communication control method using the token passing bus access method described above, when a broadcast data frame is transmitted, the receiving station does not transmit a response frame in response to the broadcast data frame, so the communication control method uses the conventional token passing bus access method. Broadcast data/
A station transmitting a frame will transmit the frame without being able to confirm how many stations have correctly received the frame. Therefore, a simultaneous broadcast data frame has the disadvantage that it becomes a data frame with poor communication quality compared to other frames.Furthermore, regarding the transmission of an immediate response data frame, a disadvantage is that it is not possible to transmit a simultaneous broadcast data frame. There is.

An object of the present invention is to provide a communication control method that improves communication quality even for such simultaneous broadcast data frames, and also enables simultaneous broadcast data frames to be transmitted even for immediate response data frames. .

[Means to solve the problem]

In the communication control method of the present invention, each station connected to a bus-type communication medium has three pieces of address information: a preceding station address, an own station address, and a succeeding station address, and a logical ring is formed on the network using the address information. The station that owns the token frame indicating the transmission right performs communication by transmitting a data frame, and after the transmission of the data frame is completed, the token frame is transmitted from the previous station to the own station based on the three address information. When a broadcast data frame is received, the transmitting station in the broadcast data frame If the information indicating the address matches the preceding station address information held by the local station, after receiving the broadcast data frame, the station transmits a response frame addressed to the station that transmitted the broadcast data frame, and If the information indicating the transmitting station address of the broadcast data frame does not match the preceding station address information held by the own station, the response frame for the broadcast data frame that matches the preceding station address information held by the own station is After confirming that the preceding station has transmitted the broadcast data frame onto the communication medium, the response frame is transmitted to the station that transmitted the broadcast data frame.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

1 and 2 are a schematic diagram of a network system using a token passing bus access method and a diagram of a communication frame format, respectively, for explaining a first embodiment of the present invention.

As shown in FIG. 1, in the network system based on the token passing bus access method, each station (A to E) 1 to 5 is connected to a communication medium 6. Each station 1~
5 has 3 addresses: preceding station, own station, f&following station 0. For example, "A" station 1 has "D'" as the preceding station address.
It will have the address of station 4 and the address of "B" station 2 as the subsequent station address. Other stations also have three addresses in the same way. Using these address information, a logical ring is formed on the network, and token frames are received and delivered in the order shown in the figure.

Further, as shown in FIG. 2, the communication frame 7 used in this embodiment has a control field 8, and the type of frame is defined by this control field 8. Broadly speaking, there are two types of frames; one is a control frame for controlling the logical ring. This includes the token frame. The other one is a data frame, which is used for information communication between stations. This data frame further includes three types of frames. The first one does not require an immediate response to the transmission of a data frame, the second one requires an immediate response from the destination station to the transmission of a data frame, and the third one does not require an immediate response to the transmission of a data frame. This is a response frame to a request. Note that an immediate response means that the station that receives the data frame immediately transmits a response frame on the spot. Hereinafter, in this example,
It is assumed that data communication is performed using this immediate response request data frame.

Further, the frame 7 has a destination address field 9 and a source address field 10, the destination address field 9 is set with the address of the shipping department, and the source address field 10 is set with the address of the transmitting station. Ru. At this time, the data frame in which all bits are set to the value "1" in the destination address field 9 becomes a broadcast data frame, and all stations 1 to 5 on the network receive and receive the data frame. This simultaneous broadcast data frame is a data frame used when a transmitting station sends data to all other stations. Note that 11 is a data field, and 12 is Fe2.

FIG. 3 is a communication control flow diagram for explaining the first embodiment of the present invention.

As shown in FIG. 3, this embodiment shows the procedure for transmitting a response frame when a simultaneous broadcast data frame is received.

Now, it is assumed that station 03 on the network described above holds a token frame and transmits a simultaneous broadcast data frame. As mentioned earlier, this data frame is an immediate response request data frame. The remaining A,
Stations B, D, and E 1°2.45 receive this frame, but know by the frame's control field 8 that it is an immediate response data frame. Further, the destination address field 9 indicates that the frame is a broadcast frame, and the source address field 10 indicates that the frame was transmitted from station 03.

First, station E will be explained. In this case, according to the processing flow shown in FIG. 3, as a result of the determination at node N1, the processing proceeds to node N2. The source address of the received broadcast data frame is the address of station 03, and for station 8 station 5, station 03 is located as the preceding station, so the determination of node N2 is Y.
It becomes es. This causes the process to proceed to node N5.
Node N5 transmits a response frame, setting the source address of the transmitted broadcast data frame in the destination address field 9 of the response frame. This completes the process of transmitting a response frame to the simultaneous broadcast data frame in the eight stations 5.

Next, station D will be explained. In this case, when station D receives the same broadcast data frame as station E, the process proceeds to node N2 in the processing flow.
Since station 3 is not the preceding station of station 0 and 4, the determination is NO.
Processing proceeds to node N3. Node N3 receives response frames transmitted from other stations in response to the broadcast data frame. In other words, station D is the first 8 stations 5 based on the positional relationship.
will receive the response frame sent from. When this response frame is received, processing proceeds from node N3 to node N4. Node N4 determines whether the source address of the received response frame matches the preceding station address of its own station. In this case, as is clear from FIG. Because it is a leading station,
Yes. As a result, processing proceeds to node N5. Further, as described above, the response frame is transmitted at the node N5, and the series of processing for the broadcast data frame is completed.

Next, station A will be explained. Station A 1 also proceeds to node N3 in the same way as station 0 4, but the first response frame it receives is the one sent by station 8 5, and station 8 5 is not the preceding station for station A 1. Therefore, in response to reception of the first response frame, the node N4 makes a negative determination and returns to the node N3 again. The next response frame received will be the one transmitted by station 04. This 0 station 4 is A
This is the preceding station of station 1, and at this time, the determination is Yes at node N4, and the process proceeds to node N5. Then, station A 1 also transmits a response frame and ends the process.

The remaining eight stations 2 proceed in the same manner as A station 1, and when they receive the response frame transmitted by A station 1, the process proceeds to node N5 and transmits the response frame.

In short, while receiving response frames from each station, station 03, which is the source of the broadcast data frame, confirms that it has received a response frame from station 8, which is the preceding station of station 03. This indicates that responses from all stations have been completed.

The above is the procedure for transmitting a response frame regarding a broadcast data frame.

FIG. 4 is a communication control processing flow diagram for explaining a second embodiment of the present invention.

As shown in FIG. 4, this embodiment shows a procedure for transmitting a response frame to a broadcast data frame, and has basically the same system configuration as the first embodiment described above. The difference between this embodiment and the first embodiment is the processing flow and the types of frames handled. In other words, in the first embodiment, the data frame is an immediate response request data frame, and immediate responses are also made to broadcast data frames, whereas in this embodiment, simultaneous broadcasts are made for data frames that do not have an immediate response. It is also possible to deal with data frames. Therefore, the response transmission procedure for the simultaneous broadcast data frame of this embodiment is as follows:
The processing flow is obtained by adding node 0 to the processing flow of FIG. 3. Hereinafter, only the differences from the first embodiment will be described.

First, when a transmitting station transmits a simultaneous broadcast data frame,
If a response frame is required, it is transmitted as an immediate response data frame as in the first embodiment. On the other hand, if a response from each station is not required, the data frame is not transmitted as an immediate response data frame.

Next, the transmitting side determines whether the frame received at node NO is an immediate response data frame based on the processing flow of FIG. 4. At this time, if Yes, the process advances to node N1, and if No, the process advances to node N6 and ends the process.

When proceeding to node N1, the subsequent processing is performed based on the same flow as in the first embodiment, so the explanation thereof will be omitted here.

〔Effect of the invention〕

As described above, the communication control method of the present invention can sequentially receive response frames from each station in response to a broadcast data frame, and therefore has the effect of improving the quality of transmitted frames. Furthermore, since the present invention can receive response frames from all stations in the order of the logical rings, it is possible to trace which stations are connected to the network at a certain point in time and in what order the logical rings are configured. This has the advantage that it can be used for network management and monitoring. Furthermore, if the present invention does not return a response frame when it is not an immediate response frame, it can be used to transmit information that does not require a response frame from each station as in the past, and to trace the previous network state. Since the simultaneous broadcast data frame can be used for different cases, such as when a response frame is required from each station, such as when a response frame is required from each station, there is an effect that efficient information transmission becomes possible.

Token Passing Bus for Illustrating Examples,
A schematic diagram of a network system using the access method and a format diagram of communication frames; FIG. 3 is a communication control processing flow diagram for explaining the first embodiment of the present invention;
FIG. 4 is a communication control processing flow diagram for explaining a second embodiment of the present invention.

1-5...Network station, 6...Communication medium (bus), 7...Communication frame, 8...Control field,
9... Destination address field, 1o... Source
address field, 11... data field,
12...Fe2. No-N6...Node.

Claims (1)

[Claims] Each station connected to a bus-type communication medium has three pieces of address information: a preceding station address, a local station address, and a succeeding station address, and a logical ring is formed on the network using the address information, and a token frame indicating the transmission right is created. The station that owns the station communicates by transmitting a data frame, and the token frame is transmitted from the preceding station to the own station and from the own station to the succeeding station based on the three address information after the data frame transmission is completed. When a broadcast data frame is received, the information indicating the transmitting station address in the broadcast data frame is transferred to the local station. If the address information of the preceding station matches the address information of the preceding station, after receiving the broadcast data frame, a response frame is sent to the station that transmitted the broadcast data frame, and the transmission station address of the broadcast data frame is transmitted. If the information indicating this does not match the preceding station address information held by the own station, a response frame for the simultaneous broadcast data frame that matches the preceding station address information held by the own station is transmitted from the preceding station onto the communication medium. A communication control system characterized in that, after confirming that the broadcast data frame has been transmitted, a response frame is transmitted to the station that transmitted the broadcast data frame.