JPH04150433A - Inter-lan coupling device - Google Patents

Abstract

PURPOSE:To reduce the waiting time at a transmitting station by making an arbitrary station belonging to one LAN to send a transmission frame containing the addresses of its own and transmitted stations to a transmission line at the moment the arbitrary station obtains a token when the arbitrary station wants to transmit information to a station belonging to another LAN. CONSTITUTION:The 1st and 2nd LANs 11a and 11b adopt the same token bus system. When information is transmitted between each station, a transmitting station sends a transmission frame containing the addresses of the transmitting and transmitted stations and data to a transmission line at the moment the transmitting station obtains a token. For example, an MPU 17 waits for a response frame 16 from the transmitted station 13b while the MPU 17 holds the token when the control code C of the transmission format 15 sent to the 2nd LAN 11b is the logical link controlling system of Type 3. Upon receiving the frame 16, the MPU 17 terminates the transmitting job and gives the token a the next station 13b. Therefore, the waiting time for the response frame at the transmitting station is remarkably reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an inter-LAN coupling device that interconnects a plurality of LANs.

(Prior art) In a LAN (Local Area Network) where multiple computers and various control devices are connected through the same transmission path and information is communicated between stations made up of these devices, information is transmitted over the common transmission path. One of the international standards that defines a media access (MAC) control method for determining which stations can transmit information is the token bus method of the IEEE (Institute of Electronic Engineers of America) 802.4 standard. In addition, as a standard for the upper layer protocol that is combined with this, IE defines the logical link control (r, LC) method between two communicating stations.
There is an EE 802.2 standard.

Stations belonging to the same LAN communicate with each other according to the above-mentioned media access control method and logical link control method.
(token) and exchanges information with the source station.

Furthermore, there are three types 1 to 3 as logical link control methods. Type 1 is a normal method in which when one station secures a token, it sends out a transmission format that incorporates data specifying the source station onto the transmission path, and when the sending process is completed, the token is transferred to the next station. be. On the other hand, in type 3, one station acquires a token, sends out a transmission format that incorporates data specifying the source station on the transmission path, and continues until it receives a response from the source station. This is a method of holding tokens. By holding the token until receiving a response from the source station in this manner, a response from the source station can be obtained immediately. Furthermore, if there is no response, the transmission format with the same content can be sent again immediately. Therefore, by adopting this type 3 logical link control method, the response waiting time at each station making up the LAN is shortened, so that the information processing speed can be improved. Therefore, this logical link control method is often employed in LANs for real-time control.

On the other hand, in an advanced information processing society, multiple independent LANs are connected using inter-LAN coupling devices, making it possible to transmit information from stations belonging to one LAN to stations belonging to another LAN. It is proposed to do so. For example, as shown in FIG. 6, a plurality of stations 2a,
Three LANs 1a, 1b, and 1c, in which LANs 2b and 2c are connected to transmission lines 3a, 3b, and 3c, respectively, are connected by two inter-LAN coupling devices 4.

L that connects LANs with different logical link control methods
As the inter-AN coupling device 4, a gateway device 4a as shown in FIG. 7 is used. This gateway device 4
As shown in the figure, a performs protocol conversion between the first LAN and the second LAN at all stages from the lowest physical layer to the highest application layer to enable information transmission between the LANs. ing.

However, as shown in the figure, since the protocols at all stages are converted to the protocols of the other party, the conversion takes a long time and the responsiveness is poor, so that this method cannot be used in the system that requires the above-mentioned real-time control.

Further, a bridge device 4b as shown in FIG. 8 is used as a device for connecting LANs using the same logical link control method. In this bridge device 4b, as shown in the figure, media access (MAC
) Since they are connected to each other at the control sublayer stage, there are fewer protocol conversions and there is an advantage of excellent responsiveness. The bridge device 4b having such a configuration is particularly referred to as a MAC bridge device.

However, even in this bridge device 4b, both LAs
If N adopts the type 3 logical link control method described above, the following situation will occur.

That is, in FIG. 6, for example, when transmitting data from one station 2a belonging to LAN 1a to station 2c belonging to LAN 1c, the transmitting station 2a captures the token and outputs the transmission frame to the transmission path 3a. , source station 2
While a holds the token, the multi-stage bridge device 4
The terminal waits for a response from the source station 2c of the final stage LAN 1c connected to the terminal. Therefore, the response time becomes longer, resulting in a significant reduction in transmission responsiveness and transmission efficiency.

In order to eliminate such inconveniences, the type 3 logical link control method described above is adopted for data transmission between stations within the same LAN, and data transmission between stations on different LANs is performed from the source station. Type 1 where there is no need to wait for the response of
It is conceivable to adopt the following logical link control method. In other words, depending on which LAN the source station belongs to,
Adopt different logical link control methods.

However, if it is known from the beginning of the system design that multiple LANs will be connected, each LAN will have the type 1
It is possible to incorporate two types of logical link control methods, type 3 and type 3, and use them properly as necessary.
If LANs that already have only the Type 3 logical link control method are connected, the above-mentioned problem will occur, so as a practical matter, it has not been possible to connect existing LANs without deteriorating their functionality.

(Problem to be solved by the invention) In this way, the conventional LA that connects multiple LANs
In the N-to-N coupling device, when connecting LANs that adopt the type 3 logical link control method, in which the source station continues to hold the token until it receives a response from the destination, the response performance is poor and real-time control is difficult. There was a problem that it could not be adopted in systems that required .

The present invention was made in view of these circumstances, and
When a transmission frame to a different LAN is received, by first sending a response to the source station, the waiting time at the source station can be shortened, and the type 3 logical link control method can be maintained. It is an object of the present invention to provide an inter-LAN coupling device that can realize high-speed information transmission between stations belonging to different LANs and easily realize a system requiring real-time control.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention adopts a token bus method, and in information transmission between each station, an information transmitting station receives a response to transmitted information. In an inter-LAN coupling device that connects multiple LANs using a logical link control method that holds tokens until
A belonging LAN storage unit that stores information for determining whether it belongs to N, and when receiving a transmission frame containing the source and destination addresses sent from an arbitrary station, the source and destination included in the corresponding transmission frame. Affiliation L to determine the LAN to which each address belongs from the information in the LAN storage unit.
When the affiliated LANs determined by the AN determining means and the affiliated LAN determining means are different from each other, the response reply means for returning a response to the source station and the affiliated LANs determined by the affiliated LAN determining means are different from each other. If the transmission frame is different, the transmission frame relay unit is provided with a transmission frame relay means for outputting the received transmission frame to the LAN to which the transmission destination address belongs, and a response reception means for receiving a response from the transmission destination station of the transmission frame.

(Function) In the inter-LAN coupling device configured as described above, when any station belonging to one LAN transmits information to a station belonging to another LAN, when it captures a token, A transmission frame containing the own station (source) and destination address and information is sent to the transmission path. Then, L
The inter-AN coupling device receives the transmission frame and determines whether the destination station belongs to another LAN from the source and destination addresses. If it belongs to another LAN, it will send a response to the source station. Then, the received transmission frame is sent to the transmission path of the LAN to which the destination station belongs. Then, it waits for a response from the destination station.

In other words, since the source station receives a response when the transmission frame reaches the inter-LAN coupling device, the waiting time from information transmission to response reception is limited to the time it takes to receive a response from a destination station belonging to another LAN. The waiting time can be significantly reduced compared to the previous one.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic diagram showing the entire system incorporating the LAN coupling device of the embodiment. The system of this embodiment has two LAs, a first LAN 11a and a second LAMllb.
LAN, and one inter-LAN coupling device 12 that connects them. 1st. Second LAN11a,llb
In each case, a plurality of stations 13a, 13a ・
...13b, 13b, ... are each one transmission line 1
4a and 14b. The inter-LAN coupling device 12 is connected to each transmission line 14a, 141).

1st. The second LANs 11a and 11b employ the same transmission method. In other words, when a token bus method is adopted and information is transmitted between each station, when the source station captures a token, it sends a transmission frame containing the source and destination addresses and data (information) to the transmission path. A type 3 logical link control method is adopted in which the token is held until a response is received from the destination station.

Note that, if necessary, it is also possible to adopt a normal type 1 logical link control method in which tokens are transferred immediately after data is sent.

When transmitting data from one station 13a, 13b to another station, a transmission frame (MAC frame) 15 sent to transmission paths 14a, 14b is configured as shown in FIG. That is, the preamble P is located at the beginning, followed by the send delimiter SD and frame control FC.
followed by the destination address D that specifies the destination station.
A and a transmission source address that specifies the transmission source station are stored. Additionally, the destination service access point DSAP
and the source service access point 5SAP, in which the control code C is stored. This control code C is a code indicating the above-mentioned logical link control method, and is composed of 8 bits as shown in FIG. As shown in FIG. 4, if the control code is set to C in [1110P/P11ACn, it indicates a type 3 logical link control method. This control code C is followed by the data to be transmitted, and finally a frame check sequence F
C8 and end code ED are included.

On the other hand, the destination station that has received the transmission frame 15 addressed to itself outputs the response frame shown in FIG.

This response frame 16 has the same structure as the transmission) I node 15, but instead of the data of the transmission frame 15, a response status STS indicating that it is a response frame is incorporated.

The inter-LAN coupling device] 2 is configured as shown in FIG. 17 in the figure is an MPU that performs various information processing controls.
(Microprocessor), and is composed of a commercially available LSI such as Intel's 800186. This M
The PU 17 connects to the EFROM 19. via the dedicated bus 18. R.A.
Controls M20 and buffer gate circuit 21.

As is well known, the EFROM 19 is formed of an ultraviolet-erasable storage element LSI, and has an area for storing programs executed by the MPU 17 and an associated LAN storage section 19a. This belonging LAN storage section 19a has a first L
The addresses of all stations 13a belonging to AN 11a and the second
The addresses of all the stations 13b belonging to the LAN 11b are stored in a table format, and the destination address DA and source address SA read from the received transmission format 15 correspond to which LAN 11a.

You can instantly determine whether you belong to 11b. In addition, 20E
The reason why the FROM 19 is made of an ultraviolet erasable type is to enable the program to be easily changed, and it is not limited to an ultraviolet erasable type memory element as long as a program can be stored.

The RAM 20 temporarily stores various variable data when the MPU 17 executes various information processing. And R
Each address area 20a temporarily stores the destination address DA and source address SA read from the transmission frame 5 in the AM20.

20b is stored.

A common bus 22 is connected to the buffer gate circuit 21 in addition to the dedicated bus 18.
It has the function of separating the

In addition to the buffer gate circuit 21, the common bus 22 includes a first TBC 23a, a second TBC 23b, and an RA.
M24 is connected.

Each TBC 23a, 23b has the above-mentioned IEE8 (1
This is a token bus controller (TBC) that controls the operation of the token bus method defined in the 2.4 standard, and is configured with a commercially available LSI such as the MCEi8824 manufactured by Motorola. And the first and second TBC23a, 2
3b is the first. Second transmitter/receiver circuit (CBM) 25
The first and second LANs 11a and llb are controlled via the first and second LANs 11a and 25b.

1st. The second transmitting/receiving circuits 25a and 25b are connected to each LAN 11.
This is a transmitting/receiving circuit that has a function of modulating and demodulating the transmission format and response format input and output to and from the transmission lines 14a and 14b, and is constructed of a commercially available LSI such as MC88194 manufactured by Motorola.

Further, the RAM 24 stores the received transmission format 1.
This is a rewritable storage element that temporarily stores a transmission format to be transmitted from the first LAN 11a to the second LAN 11b or from the second LAN 11b to the first LAN 11a beyond the LAN affiliation.

Next, the LAN coupling device 12 configured as shown in FIG.
In the system shown in FIG. 2, in which a station 13a belonging to a first LAN 11a is connected to another station 11a or a second L station 13a belonging to the same first LAN 11a, for example,
The operation of each part when transmitting data to the station 13b belonging to AN11b will be explained in order.

■ First, when station A belonging to the first LAN 11g captures the token circulating within the first LAN 11a,
Transmission format 1 shows the data to be transmitted as shown in Figure 3.
In addition, the control code C shown in FIG. 4, which shows the type 3 logical link control method, is set in the data area of No. 5, and the destination address DA indicating the source station and the source address indicating the own station are set. SA is incorporated and this transmission format 15 is sent to the transmission path 14a.

Note that when specifying a type 1 logical link control method in which the token is transferred immediately after transmitting the transmission format 15, a code corresponding to the type 1 logical link control method is set in the control code C.

■ When the transmission format 15 is sent to the transmission path 14a of the first LAN 11a, the first transmission/reception circuit (CBM) 25a in the inter-LAN coupling device 12 receives the transmission format 15, further demodulates it and 1 TBC23a
Send to.

(2) The first TBC 23a converts serial data in transmission format 15 received from the first transmitting/receiving circuit 25a into parallel data, stores it in the RAM 24, and sends a reception interrupt signal INa to the MPU 17.

- The MPU 17, to which the reception interrupt signal rNa from the first TBC 23a has been input, reads the transmission destination address DA of the received transmission format 15 temporarily stored in the RAM 24 via the Paffer gate circuit 21, and reads the transmission destination address DA of the received transmission format 15.
The belonging LAN storage unit 19a of the OM 19 is searched to find out which LAN 11a or llb the corresponding destination address DA belongs to.

■ If the destination address DA belongs to the same first LAN 11a as the source address SA, there is no need to relay the transmission format 15 with this inter-LAN coupling device 12, so the transmission format 1 temporarily stored in the RAM 24
5 is cleared to end this reception process.

■ If the destination address DA does not belong to the same first LAN 11a as the source address SA, check the 8-bit data of control code C of transmission format 15 to determine whether the logical link control method is type 1 or type 3. Determine.

(1) If it is type 3, a command to send the response frame 16 to the source station A is output to the first TBC 23H. The first TBC 23a creates a response frame 16 shown in FIG. 5 and sends it to the transmission line 14a of the first LAN 11a. At the same time, it outputs a command to the second TBC 23b to transmit the received transmission frame 15 to the second LAN 11b.

(2) If it is type 1, there is no need to send the response frame 16 to the source station A, so the first LAN 11
It outputs a command to the second TBC 23b to transmit the received transmission frame 15 to the second LAN 1 l b without transmitting anything to the second TBC 23b.

That is, in this case, only the relay processing of the transmission frame 15 is performed.

■ Station 1 of transmission source A belonging to the first LAN 11a that received the response frame 16 from the inter-LAN coupling device 12
Station 3a determines that the data transmission is complete and transfers the token to another adjacent station 13a.

■ On the other hand, the second TB receives a transmission command from the MPU 17.
When the C23b acquires the token on the second LAN 11b, it sends the transmission format 15 temporarily stored in the RAM 24 to the transmission path 14b.

If the control code C indicates type 3, the destination station 13b belonging to the second LAN 11b which received the transmission frame 15 from the inter-LAN coupling device 12 transmits the response frame 16 shown in FIG. 5 to the transmission path 11b. Send to.

(2) If the control code C of the transmission format 15 sent to the second LAN 11b is a type 3 logical link control method, the MPU 17 waits for the response frame 16 from the destination station 13b while holding the token. When the response frame 16 is received, the transmission task is ended and the token is transferred to the next station 13b.

Note that if the response frame 16 from the destination station is not received within a predetermined period of time, the same transmission frame 15 is sent to the transmission path 14b again.

Furthermore, if the control code C of the transmission format 15 sent to the second LAN 11b is a type 1 logical link control method, there is no need to wait for the response frame 16, so the token is sent to the next station immediately after the transmission format 15 is sent. 13
Delegating to b, the sending task is completed.

Note that from the station 13b of the second LAN 11b to the first LAN
The processing operation described above also applies when transmitting data to the station 13a of the station 11a.

According to the inter-LAN coupling device configured in this way, when transmitting data to a station belonging to another LAN using the type 3 logical link control method, the source station assembles the data into a transmission frame. The token is transferred to the next station after receiving the response format from the destination station. In this case, the response format is not sent from a destination station belonging to another LAN, but from the inter-LAN coupling device. Therefore, the time required for the inter-LAN coupling device to capture a token within the LAN to which the destination station belongs, and the time required for the transmission frame to reach the destination station and for the response frame to return to the inter-LAN coupling device can be omitted. The waiting time of the source station can be significantly reduced.

In other words, the source station transmits data to other LLANs in approximately the same amount of time as it takes to transmit data to each station in the LAN to which the source station belongs.
Data transmission is possible using the type 3 logical link control method with stations belonging to the AN. However, even in a system configured with multiple LANs as shown in Figure 2,
Real-time control processing using type 3 logical link control method becomes possible.

Furthermore, if the LAN coupling device 12 does not receive the response frame 16 from the destination station within a predetermined period of time, it sends the same transmission frame 15 to the transmission path again, so that the data is correctly transmitted to the destination station. As with the conventional type 3 logical link control method, the reliability achieved is sufficiently ensured.

Note that the present invention is not limited to the embodiments described above. In the embodiment device, the LA of EPROM19 is
Each station 13a is stored in the N storage section 19a.

Although the LANs 11a and 1.1b of the LANs 13b are stored in a table format, the LAN storage section may be formed in a separate EPROM, for example. Furthermore, it is also possible that a keyboard input terminal device or the like is separately connected to the inter-LAN coupling device 12, so that the operator can enter the LAN to which the user belongs manually in advance. Also,
The MPU 17 connects to each LAN via each TBC 23a and 23b.
11 a.

For example, the addresses of the stations 13a and 13b of 11b are read from the source address SA of the transmission frame 15, and
The affiliated LAN storage unit may be formed using a learning algorithm method that writes to the AM24.

Furthermore, in this embodiment, the first. 2nd LAN1
Although a system composed of two LANs 1a and llb has been described, it goes without saying that the present invention can be applied to a system in which three or more LANs are connected in series using a plurality of inter-LA coupling devices.

[Effects of the Invention] As explained above, according to the inter-LAN coupling device of the present invention, when a transmission frame to a different LAN is received,
A response is sent to the source station without counting, and at the same time, the received transmission frame is sent to the LAN to which the source station belongs. Therefore, the waiting time for response frames at the source station is significantly reduced, and while maintaining the type 3 logical link control method, information transmission can be realized at high speed between stations belonging to different LANs, and real-time control can be achieved. It is possible to realize a system that requires

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1 to 5 show an inter-LAN coupling device according to an embodiment of the present invention. FIG. 1 is a block diagram showing a schematic configuration, and FIG. 2 is a diagram showing the entire system. FIG. 3 is a diagram showing the transmission format, FIG. 4 is a diagram showing the bit structure of the control code, FIG. 5 is a diagram showing the response format, and FIG. 6 is a diagram showing a general system. Schematic diagram, 7th
8 and 8 are block diagrams showing a schematic configuration of a conventional LAN coupling device. 11a--First LAN, 1lb--Second LA
N. 12-LAN coupling device, 13a, 13b--station, 14a, 14b--transmission line, 15--transmission format, 16--response format, 17...-MP
U.

Claims (1)

[Claims] A token bus method is adopted, and a logical link control method is adopted in which an information transmitting station holds a token until it receives a response to transmitted information in information transmission between multiple LANs. In the LAN coupling device to be connected, there is a belonging LAN storage unit that stores information on which LAN the addresses of all the stations constituting each LAN belong to, and a source and destination address sent from any station. When a transmission frame containing a transmission frame is received, each belonging L of each source and destination address included in the transmission frame is
Belonging L that determines the AN from the information in the belonging LAN storage unit
When the affiliated LANs determined by the AN determining means and the affiliated LAN determining means are different from each other, a response reply means for returning a response to the source station, and each affiliated LAN determined by the affiliated LAN determining means are different from each other. The transmission frame is characterized by comprising a transmission frame relay means for outputting the received transmission frame to a LAN to which the transmission destination address belongs when the transmission frame is different from each other, and a response reception means for receiving a response from the transmission destination station of the transmission frame. LAN coupling device.