JPH02270437A - Inter-network connector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to a ring local area network (LAN).
), in particular, an inter-network transfer frame transmitted from this inter-network connection device to a ring-type LAN is removed from the network after going around the ring-type LAN. The present invention relates to an inter-network connection device with functions.

[Conventional technology]

In recent years, there has been an increasing demand for coordination of information and communications within premises, and LANs have begun to become popular. LAN standardization activities are currently underway in the IEEE, ANSI, ISO, etc., and several standards have already been established.

A ring-type LAN is a typical LAN topology that has already been standardized.

This ring type LAN medium access control (MAC:Me)
dia Access Control) method,
Token ring method or FDDI (Fiber
Distributed Data Interface
) method is attracting attention. In these systems, transmission rights are transferred between nodes by circulating control frames called tokens on a ring network. A node that has generated a frame that it wants to transmit captures a token, transmits the frame, and after the transmission is completed, releases the token and passes the transmission right to another node. It is necessary for this transmitting node to re-receive the frame transmitted by itself after going around the ring network and remove it from this ring network.

Furthermore, in the past, it was possible to accommodate all information devices such as hosts and terminals with one LAN.

However, as the amount of information processing increases, the number of information devices increases and the scope of use becomes broader, making it difficult to accommodate all of these devices in one LAN. Furthermore, it is not appropriate from the viewpoint of functionality and performance to realize systems with different usage patterns and processing contents using a single LAN. Therefore, a large number of various LANs have come to be installed within the premises.

Against this background, there has been a demand for communication from a node belonging to one LAN to a node belonging to another LAN. In order to control communication between different LANs, an inter-network connection device is required.

FIG. 14 is a diagram showing an example of a network configuration when LANs are interconnected. This network is LAN
I and LAN II are connected via an inter-network connection device (bridge) l, and nodes 2 to 4 are connected to the LAN II.
The nodes in LAN II, nodes 5-7, are nodes in LAN II. The bridge 1 is also a node belonging to both LAN I and LAN 1, and has a MAC bridge function for controlling the transmission and reception of inter-network transfer frames for mutual communication between nodes 3 and 5, for example. It is assumed that node addresses 1lhl to 7 are assigned to these nodes 1 to 7, respectively.

In such an interconnection network, when a frame is sent from a node in LANI to a node in LAN II, the frame is transferred via a bridge l having an MMC bridge function.

FIG. 15 shows another example of a network configuration in which a plurality of networks are interconnected.

A bridge station 8.9 is provided in the ring type LAN II [()-Kunring LAN) together with a node 10.11. LAN I [[LAN rV, V is]
They are connected via ridge stations 8 and 9, respectively.

LAN IV has terminal 12.13.14------
--- is provided, and LAN V has terminal 15.16.1.
7...---1--- are provided respectively. LAN
Intercommunication of data between I[I, IV and V takes place via a bridge station 8.9.

[Problem to be solved by the invention]

FIG. 16 is a diagram showing a frame format applied to an FDDI type LAN.

As shown in the figure, this frame includes a preamble PA for achieving phase synchronization upon reception, a start delimiter SD indicating the start position of the frame, a frame control FC, a destination node address DA, and a source node address SA.

Information section INFO, frame check sequence FCS, end delimiter 80 indicating the end position of the frame. and frame status FS.

In a general node accommodated in an FDD I LAN, the source node address SA of the received frame
If it matches the own node address, the received frame is determined to be a frame transmitted by the own node and is deleted. Alternatively, as disclosed in Japanese Patent Application Laid-open No. 61-084940, after transmitting a frame from its own node, a counter counts the ring travel time, and - the received frame that arrives after the reverse time elapses is deleted as the transmitted frame from the own station. Was.

However, like such a normal node, the first
When the bridge 1.8.9 shown in FIGS. 4 and 15 is operated, the following problem occurs.

In the interconnection network shown in FIG. 14, for example, from node 3 in LAN I to LA
When forwarding a frame to node 5 in N II, node 3 sets the source node address SA to 3. Create a frame with the destination node address OA as N115 and send it to the LAN
Send within I. And this frame as bridge 1
The data is sent to the LAN II via the LAN II, and the target node 5 receives it.

At this time, bridge l needs to erase this transfer frame after it has circulated through the ring (LANn).

However, as mentioned above, when Bridge 1 operates in the same way as other general nodes, Bridge 1 identifies and erases the frame sent by its own station because the source node address SA in the received frame is its own node number. configured to do so. Therefore, the source node address SA is
It is not possible to erase the above-mentioned transfer frame as it is, and this transfer frame continues to circulate around LAN n.

The same is true for transferring a frame from node 5.6.7 in LAN I to node 213.4 in LAN I.

Therefore, as another method, a method of reconstructing the received frame as shown in FIG. 17 can be considered. When bridge l receives a transfer frame from node 3 to node 5 (see FIG. 16), destination node address DA=N15. Source node address 5A=
lk3. The information INFO is assumed to be an information section INFO2. Furthermore, a method is conceivable in which a new transfer frame is assembled by rewriting the source node address SA to Nll (address of bridge 1) and the destination node address DA to 5, and transmitting this transfer frame within LAN I. In this case, the destination receiving node 5 receives the information part IN in the received frame.
Analyze the contents of FO2 and find the source node address SA=m
You will know 3. However, in order to use this method, each node within the LAN must have a function to analyze not only the source address SA but also the source address from the contents of the information section INFO□, and it is compatible with two types of frame formats. The system becomes complicated.

In addition, in the method of monitoring and erasing the reception timing of frames sent by the local station using a counter, if the ring-to-ring time changes due to the addition or deletion of nodes in the network, the set value of the one-to-one time for all nodes is changed one by one. You have to do it, and it takes a lot of work.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an inter-network connection device that does not require changing the frame format when transferring frames between interconnected LANs. Another object of the present invention is to provide an inter-network connection device that is not affected by changes in network configuration.

[Means to solve the problem]

FIG. 1 is a diagram illustrating the principle of the present invention.

The inter-network connection device according to the present invention connects local area networks (LANs) shown in FIGS. 14 and 15, and transmits transfer frames between the LANs.

It performs reception control.

According to the first invention, the destination of an inter-network transfer frame whose destination is a node in a ring type local area network and whose source is a node in another local area network is stored, and the destination is transmitted to the ring type local area network. When the destination in the inter-network transfer frame received from the transmitting means 101, 101'' and the ring-type local area network matches the stored destination, this inter-network transfer frame is transferred from the ring-type local area network. and removing means 100.100'' for removing.

According to the second invention, an inter-network transfer frame whose destination is a node within a ring-type local area network and whose source is a node within another local area network is transmitted to the ring-type local area network following a dummy frame. means 101.101', detecting a dummy frame received from the ring local area network after transmitting the dummy frame, and removing the inter-network transfer frame received following this particular frame from the ring local area network; Removal means 100 to
゜too'.

[Operation] According to the first invention, a transfer frame passing between LANs is identified, and the destination of this transfer frame is stored.

Therefore, without changing the frame itself, the transfer frame sent by itself goes around the ring LAN,
It is possible to identify that it has been received.

Further, according to the second invention, a dummy frame for identification is transmitted prior to transmitting the transfer frame. Therefore, by detecting the reception of the dummy frame, which is this special frame, it is possible to easily detect the reception of the transfer frame transmitted by itself.

〔Example〕

FIG. 2 is a block diagram of the network connection device according to the first embodiment of the present invention.

First, in Fig. 14, the network connection device (bridge) l
When sending and receiving frames within a LAN, especially,
Bridge l transfers inter-network transfer frames sent from node 3
An example will be explained in which the received data is received at the node 5 and transferred to the node 5.

The frame transmitted from node 3 is sent to frame receiver 23
The signal is received by the frame, and phase synchronization is achieved using the preamble PA of the frame (see FIG. 16) to create a timing signal. The received frame is input to the reception control section 24, reception buffer 25, and selector 29. The received frame is copied to the reception buffer 25. The reception control unit 24 detects the leading SD of the received frame under timing control by the frame receiver 23, identifies the destination address DA and the source address SA, and notifies these to the microprocessor (MPU) 20 via the control bus 42. The microprocessor 20 instructs the receive frame in the receive buffer to be transferred to the system memory 21.

The system memory 21 contains each I system related to LANI and n? 11m information (frame format information and format conversion information of LAN I, LAN H, etc.) and nodes 2 to 2 accommodated in LAN I and II.
7 address information is stored. Furthermore, received transfer frames are buffered in the system memory 21. The MPU 20 refers to the node address information in the system memory 21 and determines whether the destination address DA notified from the reception control unit 24 is the address of a node belonging to LAN I or LAN II. do. Determination of the source address SA will be described later.

If the MPU 20 determines that the destination address D is the address of a node belonging to LAN I, it is necessary to send the received frame to LAN I as is.

The selector 29 is set to select the output of the frame receiver 23 except when the bridge 1 is transmitting. Therefore, the received frame received by the frame receiver 23 is
The frame transmitter 30 sends the frame to LAN I via the selector 29 as it is. That is, the frame transmitted from node 3 will pass through bridge l.

Furthermore, the MPU 20 clears the received frame copied to the reception buffer 25.

Next, the MPU 20 sets the destination address OA to LAN I.
A case where it is determined that the node belongs to [ will be explained.

In this case, frames received from LAN I are sent to LA
This is an 8M transfer frame to N It.

When transferring a received frame from LAN I to LAN II, the MPU 20 must first convert the frame format of the received frame buffered in the system memory 21 to the frame format used in LAN II. For this reason, MPU2
0 C. Converts the received frame to the format used in LAN II while referring to the format information in the system memory 21. Then, the converted reception frame is transferred to the transmission buffer 38 via the data bus 41. M
P[I 20 instructs the reception control unit 34 to capture the token circulating around LAN II in order to acquire the transmission right of LAN IT.

Therefore, the received frame is copied by bridge 1, which is the transmission destination, and then sent out again to LAN I.
NI is circulated toward the source node 3.

The frame receiver 33 connected to the LAN [[
It operates in the same manner as the frame receiver 23 described above, and the received frames are sent to the reception control unit 34. The signal is input to the receive buffer 35° selector 43.

When the reception control unit 34 detects the token, the reception control unit 34 notifies the MPII 20 via the control bus 42 that the token has been captured.

As a result, the bridge 1 acquires the right to transmit the LAN If.

In this case, bridge 1 becomes a frame transmission source in LAN II. Therefore, the transmit buffer 38
The transfer frame sent from LAN II to LAN
When the signal goes around U and is received again at bridge l, it needs to be removed. That is, it is necessary to identify the transfer frame transmitted by itself, and for this purpose, a source address management table 39 is provided.

MP[I20 is the source address S of this transfer frame
A is stored and stored in the source address management table 39 as the transfer frame identifier (SA).

In addition, 1ro 20 is a transfer frame containing the corresponding identifier (
A command is sent to the transmission control unit 36 to send the transmission frame) to LAN II. The transmission control unit 36 switches the selector 43 to select the output of the transmission buffer 38.

Then, the transfer frame is sent to the LAN by the transmitter 40.
II.

This transfer frame is transferred from the transmitting section 40 of the bridge to the LAN.
II. Thereafter, the transmission control unit 36 controls the pattern generator 37 according to a command from the MPU 20, switches the selector 43, and selects the output of the pattern generator 37. The pattern generator 37 generates a token pattern, and as a result, a LAN II token is sent from the pattern generator 39 via the selector 43 and the transmitter 40, thereby releasing the transmission right. .

Then, the MPII 20 switches the selector 43 to the frame receiver 33.

Thereafter, the transfer frame sent from bridge 1 to LAN n is taken in by node 5, circulates around LAN U, reaches bridge 1 again, and is received by frame receiver 33.

The address indicated by the source address S^ of the transfer frame is notified to the MPU 20 via the control bus 42.

The MPU 20 activates the source address management table 39. It is determined whether the source address SA of this received transfer frame is stored in the source address management table 39.

At this time, it is determined that the source address SA of the received transfer frame is not stored in the source address management table 39, and this result is notified from the source address management table 39 to the MPII 20.

As a result, the MPU 20 detects that the received frame is not a transfer frame sent from the local station from LAN I to LAN II. Since the selector 43 has been switched to the output of the frame receiver 33, the received frame is directly sent to the LAN n from the transmitter 40.

Further, when it is determined that the source address SA of the received frame is stored in the source management table 39, the MPU 20
identifies that this received frame is a transfer frame transferred between networks from bridge 1 to LANn, and removes this frame.

In order to remove this transfer frame, the MPU 20 sends a control signal to the transmission control section 36. Transmission control section 3
6 is the source address SA (first
In order to replace the following with an idle pattern (see FIG. 6), first, the selector 43 is switched to the output of the pattern generator 37, and the idle pattern is sent to the transmitter 40. Therefore, in the frame sent to LAN n, the source address SA in FIG. 16 is replaced with an idle pattern, and the removal of the frame sent from the local station is completed.

This kind of frame removal is called stripping.

The source management table 39 in FIG. 2 will be explained in more detail below.

In the source address SA table management circuit 50 of the source management table 39 shown in FIG.
An address storage section 52 is formed for each bit, and a control flag storage section 51 is formed for each 1 bit.

The address storage section 52 stores the source address of the transfer frame.

The control flag storage section 51 stores the address storage section 52 of the relevant row.
This indicates whether the source address is registered in the frame, and is set (0-1) when transmitting a transfer frame.
) and reset (l) when the relevant frame is received.
→0) will be done.

Note that the number of bits in each row of the control flag storage section 51 is set to increase depending on the control content.

The number of rows in the address storage section 52 and the control flag storage section 51 is determined by the time t required for a transmission frame to go around the LANn, the average length l of the transmission frame, and the rotation speed (ring bit speed) of the transmission frame. For example, k = t x v / 1 is a positive integer.

In the above SA child table logic circuit 50, the address storage section 5
2 and a pointer indicating a line to be read or written in the control flag storage unit 51 is managed in a FIFO manner,
When the pointer reaches the last line, it is returned to the first line.

Further, as pointers, a transmission pointer 55 for frame transmission and a strip pointer 56 for frame stripping are used.

The transmission pointer 55 indicates the line in which the originating address of the next frame to be transmitted should be registered.

The slip pointer 56 is already in the frame of the transmitter.
This shows the line in which the originating address of the oldest unconfirmed transmission frame is registered.

When a transfer frame from node 3 to node 5 of LAN I is given to bridge 1, an instruction is given from MPU 20 to reception control section 34. When the reception control unit 34 captures the token circulating around the LAN U, the reception control unit 34 notifies the MPU 20 that the token has been captured.

As a result, a control command is given from the MPU 20 to the transmission control section, and the transfer frame is sent from the transmission section 40 to the LAN n.

At that time, the transmission source address indicated by the data SA of the transmission frame is extracted by the MPU 20, and the extracted address is written in the row indicated by the transmission pointer 55 in the address storage section 52.

Furthermore, the flag for the same row is set (0-1) in the control flag storage section 51, and the transmission pointer 55 is advanced to the next row.

Therefore, from each node in LAN I, l, AN
When different inter-network transfer frames to each node in II are received by multiple bridges 1 and sequentially sent to LAN II,
The source address of each transfer frame is sequentially registered in the address storage section 52 in the direction of the arrow shown in FIG.

Therefore, when m transfer frames are sent,
As shown in FIG. 3, the source address of each transfer frame is registered in order in the address storage unit 52, and the control flag storage unit
Then, the corresponding flag is set, and the source addresses SA in the m transfer frames are registered in the SA table management circuit 50.

Further, when the transfer frame transmitted from the frame transmitting section 40 to LAN II goes around LAN II and is received again from LAN II by the frame receiving section 33, the transfer frame's source address 5A (L
The address of the node in AN I is extracted by the IPU 20 via the reception control unit 34.

The transmission source address of the transfer frame obtained by the extraction is also given to a comparator 53 provided in the transmission source address management table 39.

The comparator 53 searches the control flag storage section 51 for all rows in the flag sent state, and searches the control flag storage section 51 for all rows in the flag sent state.
The sender address registered in the search line is read out.

Further, a match is determined between the source address read from the address storage section 52 and the source address extracted from the received transfer frame.

If Ta is found that the extracted source address does not match any of the read source addresses, the received frame temporarily stored in the receive buffer 35 received from the LAN If at this time is cleared. The received frame is then sent to the selector 43. The frame is sent directly to LAN n via the frame transmitter 40.

On the other hand, from the received transfer frame, the reception control unit 34
If the source address extracted by the MPII 20 matches any of the source addresses stored in the address storage unit 52, the address from the line indicated by the strip pointer 56 to the address line in the address storage unit 52 is The row portion is cleared by the comparator 53 as shown in FIG.

If a transfer frame sent from bridge l to LAN n does not cause a focusing error during one round of LAN n, the row indicated by the strip pointer 56 and the row where an address match is detected by the comparator 53 are Match. However, if a bit error occurs, the source address SA cannot be extracted from the received transfer frame, and the strip pointer 56 is not updated.

Therefore, after that, when a transfer frame is received normally, the address line indicated by the comparator 53 advances from the line indicated by the strip pointer 56 by the number of transfer frames in which the error occurred. A focus error in a received frame is detected by the MPU 20 based on the FCS bit in the frame, and in this case, the received frame with the error is removed from the LAN. That is, it is stripped.

Therefore, if the row of the SA child table logic circuit 50 in which the source address SA of the transfer frame in which the error occurred is not cleared, the source address of the transfer frame that no longer exists in the LAN will remain, and in the worst case In the case of S^
The management table circuit 50 overflows.

To solve this situation, the strip pointer 56
The comparator 53 clears the line from the line indicated by to the address indicated by the comparator 53.

Furthermore, the flags of those rows in the control flag storage section 51 are also reset by the comparator 53.

Then, the comparator 53 detects the match of the source address.
The PII 20 is notified of the address match. Upon receiving this, the MPU 20 requests the transmission control unit 36 to strip the received transfer frame.

When the request is given to the transmission control unit 36, the selector unit 39 is switched from the frame receiver 33 side to the pattern generator 37, and the received transfer frame at this time is transferred to the LAN.
Removed from II.

In this first embodiment, the source address of the received frame and S
Although each registered address of the A-child table logic circuit 50 is compared in order by the comparator 53 as shown in FIG. 4, it is also possible to perform these comparisons in parallel and at the same time. The selection is made in consideration of the circuit configuration, its scale, and the time required for comparison processing.

Further, in this embodiment, when the source address of the received transfer frame and the registered address match, the address storage unit 52
Although both the control flag storage unit 51 and the control flag storage unit 51 have been erased,
It is also possible to erase (reset) only the control flag storage section 51.

Furthermore, a timer area is provided in the control flag storage unit 51 of the SA child table logic circuit 50, and the sending source is configured to perform the above-mentioned erasure on the corresponding row area when time-up occurs after a certain period of time has passed since address registration. It is also possible to configure the address management table 39.

In this case, it is preferable to set the time-up time to be slightly longer than the time required for the transmission frame to circulate around LAN n.

In other words, even if a via error occurs while the transmission frame is circulating around LAN II, the corresponding registration row will be deleted on the second round, so the SA child table logic circuit 50 will not be full of registration data due to the accumulation of bit errors. This makes it possible to avoid such obstacles.

A block diagram of an inter-network connection device as a second embodiment of the present invention is shown in FIG. The embodiment shown in Fig. 5 shows the structure of the bridge 1 in the interconnection network of cylinders 14 and 15 as in Fig. 2, and the same parts as in Fig. 2 are given the same numbers. ing.

In FIG. 5, the frame receiver 23 is configured to send directly to the frame transmitter 30 via the selector 29 and to the system memory 21 via the receive buffer 25 and buses 41, 42, respectively. The frame reception control unit 24 analyzes frames circulating within LAN I. It also has a function to acquire tokens circulating within LAN I and a function to detect dummy frames, which will be described later.

The transmission control unit 26 has functions such as monitoring the reception of dummy frames and notifying the transmission frame number counter 61 of the number of frames transmitted and received following the dummy frame, and controls the timing of erasing frames.

This dummy frame is generated by a dummy pattern generator 60.

FIG. 6 is a diagram showing a frame format of a dummy frame. Dummy frame is destination node address DA
and the source node address SA and the own node address 1
is set, and a code 10 indicating that this frame is a dummy frame is set in the part corresponding to the information section INFO. By adopting such a format, it is possible to prevent the frame from being confused with a return frame addressed to the own node from the own node used for testing purposes.

The transmission frame number counter 61 is a circuit that counts the number of transmitted and received frames, and according to instructions from the transmission control unit 26 and reception control unit 24, at the time of transmission, it counts up the number of data frames transmitted following the dummy frame, and also counts up the number of data frames transmitted following the dummy frame. When receiving a frame, it has a function to count down the number of subsequently received frames transmitted by the local station.

Frame reception control section 34, frame transmission control rJ section 36
, the dummy pattern generator 70, the transmission frame number counter 71, etc. are also circuits having the same functions as each circuit described above for the ring type LAN n, so their explanation will be omitted.

The operation of the apparatus of this embodiment will be described below with reference to the drawings.

An example of a frame transmission sequence and a counter value in bridge 1 is shown in FIG. In the figure, the vertical direction is the time axis, and time passes downward. Also, the diagonal arrow indicates that the frame transmitted from the local station has gone around the ring and been received by the local station. Therefore, the left node and the right node are the same bridge l and have the same count value. Further, the flow of the processing procedure at the time of transmission in the transmission of the dummy frame by the bridge 1 is shown in FIG. 8, and the flow of the processing procedure at the time of reception is shown in FIG. 9, respectively.

Now from node 3 in ring type LAN I to ring type L
Assume that a frame is sent to node 5 in AN II. This frame circulates within LAN I, is received by the frame receiver 23 of the bridge 1, and is sent to the frame reception control section 24. The frame reception control unit 24 is notified of the destination node address OA=5, the source node address 5A=11h3, and the information INFO in the frame to the MPU 20 via the buses 41 and 42 as frame data. The MPU 20 refers to information stored in the system memory 21 and determines whether the received frame is connected to the LAN.
Check whether it is an inter-network transfer frame addressed from I to LAN II.

When an inter-network transfer frame is received, it is transferred from the reception buffer 25 to the system memory 21. The MPU converts this frame into a format for LAN II.

Then, it is transferred to the transmission buffer 38. To transmit this inter-network transfer frame to LAN n, the procedure shown in the flowchart of FIG. 8 is followed. First, the frame transmission control unit 34 monitors whether the frame reception unit 33 has acquired a token, which is the right to transmit within LAN n (step Sl), and when the frame reception unit 33 has acquired a token, it sends a message to the transmission frame number counter 71. A reset request is issued to reset the count value (step S2).

Next, the frame transmission control section 36 activates the dummy pattern generation section 70 and switches the selector 39 from the frame receiver 33 to the dummy pattern generation section 70 .

Then, a dummy frame having the format shown in FIG. 9 is generated (step S3). That is, a dummy frame is generated in which the destination node address OA is set to the own node address 1. Then, the MP stored in the transmission buffer 38
Prior to transmitting the inter-network transfer frame converted from LAN I to LAN If frame format by U20, the generated dummy frame is sent to selector 3.
0. It is transmitted to LAN If via the frame transmitter 40. (Step S4).

In response, the frame transmitter 40 starts transmitting the dummy frame from the dummy pattern generator 70 to the LAN If. The frame transmission control unit 36 monitors the transmission of the dummy frame from the dummy pattern generator 70, and when the transmission of the dummy frame is completed (step S5), the frame transmission control unit 36 switches the selector 39 to the transmission buffer 38. Read the stored data frame addressed to LAN n and send it to LAN II.

This data frame is sent to the frame receiving section 2 of LAN I.
This is an inter-network transfer frame received at 3, and the destination node address DA is a node address within LAN n (for example, floor 5).
, the source node address SA is a node address within LAN I (for example, patient 3), and this is
It is simply a format conversion.

The frame transmission control unit 36 uses this transmission buffer memo 1J3.
8, and when data frame transmission starts, it instructs the transmission frame number counter 71 to count and amplify the count value by one every time one data frame is transmitted. Step S7). This operation is repeated until all data from the transmission buffer memory 38 is completely transmitted. When the transmission of all data is completed, or even if the transmission of all data is not completed but the token holding limit time assigned to bridge 1 has elapsed, the token (access right) of LAN n is released (step S6). , ends the sending operation.

By the above-described operation, after the dummy frame is sent, the number of data frames continuously sent out is counted by the transmission frame number counter 71.

Next, the reception operation will be explained. The dummy frame and the following data frame sent from Bridge 1 are L
After going around AN II, it is received again by the frame receiving unit 33 of bridge I. The frame reception control unit 34 monitors the frame received via the frame reception unit 33 (step 511), and if the received frame is the dummy frame shown in FIG. 6 (step 512),
The frame transmission control unit 36 is notified. The frame transmission control section 36 instructs the frame transmission section 36 to discard the received dummy frame.
5, the selector 39 is switched from the frame receiver 33 to the pattern generator 37, and the received dummy frame is stripped in the same manner as in FIG. (Step 513).

When the frame reception control unit 34 receives a data frame following the dummy frame, the frame reception control unit 34 determines that if the content of the transmission frame number counter 71 is zero (
Step 515), Step 3 of issuing a frame erasure (stripping) request to the frame transmission control unit 36
16) At the same time, it issues an instruction to the transmission frame number counter 71 to count down its count value by one (step 514).

The frame transmission control unit 36 receives the frame erasure request, and
Start frame stripping. The transmission control section 36 controls the selector 39 and pattern generator 37, and performs stripping of the received frame as in FIG. 2. The above operation is repeated until the count value of the transmission frame number counter 71 becomes zero (steps S15 to S517), and when it becomes zero, the process ends (step 318). This allows inter-network transfer frames from other LAN I sent to LAN I after the dummy frame to be sent to the ring-link (without referring to the source node address SA).
It becomes possible to erase using bridge 1 after the cycle.

Above, we have explained the case where data frames are transferred from LAN I to LAN II, but in the opposite case, LA when transferring data frames from LAN
The operation of the NI side circuit is also exactly the same.

Next, a third embodiment of the present invention will be described.

FIG. 1O is a block diagram of an inter-network connection device according to a third embodiment of the present invention.

Dummy frame generator means 45 generates first and second dummy frames.

After sending out the first dummy frame, the frame transmission control unit 26.36 sends out at least one inter-network transfer frame, and then sends out the dummy pattern generation means 60', 70' and Selector 29.3
Control 9.

The frame reception control unit 24.34 controls the frame reception unit 23.
．． A first dummy frame and a second dummy frame are detected among the frames received at step 33.

The MPt 120 controls the frame transmission control section 26.36 based on the detection result of the frame reception control section 24.34, and transfers the received inter-network transfer between the first dummy frame and the second dummy frame by controlling the frame transmission control section 26.36. Erase (stripping) the frame.

Therefore, the inter-network transfer frame received during the period between reception of the first dummy frame and reception of the second dummy frame is erased.

Next, the operation of the block diagram shown in FIG. 10 will be explained.

The frame format of the dummy frame is the same as that described with reference to FIG.

Further, FIG. 11 shows an example of a frame transmission sequence in the bridge 1. In the figure, the vertical direction is the time axis, and time passes downward. Also, a diagonal arrow indicates that the frame transmitted from the local station has gone around the ring and been received by the local station.

Therefore, the left-hand node and the right-hand node represent the same bridge 1. Further, the flow of the processing procedure at the time of transmission in the bridge 1 is shown in FIG. 12, and the flow of the processing procedure at the time of reception is shown in FIG. 13, respectively.

Now, assume that a frame is transmitted from node 3 in ring type LAN I shown in FIG. 14 to node 5 in ring type LAN II. This frame is LAN
frame receiving section 23 of bridge I;
The frame is received by the frame reception control unit 24, and the destination node address DA=lk5, source node address 5A-43, and information INFO in the frame are extracted, and the bus 4L42
The MPU 20 is notified via. Then, the MPU 20 refers to the system memory 21 and determines whether the received frame is LAN.
1 to LAN II is checked, and if it is a transfer frame, the format is converted.

To transmit this frame data to LAN II, the procedure shown in the flowchart of FIG. 12 is followed.

First, the frame reception control unit 34 monitors whether a token, which is the right to transmit within LAN II, has been acquired (step 511), and the reception monitoring of the token is repeated until the token is acquired.

When the token is acquired, the frame reception control unit 34 notifies the microprocessor MPU 20 that the token has been received (step 512).

Next, microprocessor MPU 20 determines whether there is a data frame to be transmitted in system memory 21 (step 513). If there is no data frame to be transmitted, a negative determination is made, the acquired token is released (step 520), and the transmission process ends. still,
After the token is released in step 520, the processing from step 511 onward is repeated.

If an affirmative determination is made in step 513 (Is there a data frame to be transmitted?), then the microprocessor 20
Activate the dummy frame generator 45 and copy the dummy frame to the transmission sofa memory 223 (step 514)
. This dummy frame has the structure shown in FIG. 6, and the destination node address D^ and the source node address SA are both set to 1, which corresponds to node 1.

The microprocessor 20 also transfers the data frame to be transmitted to the transmission buffer memory 38 (step 5).
15). The system memory 21 contains nodes 3 to 5.
A plurality (for example, three) of format-converted data frames to be transferred are stored, and the microprocessor 20 reads one of these frames and stores it in the transmission buffer memory 38.

Note that this data frame is the data frame itself sent from node 3, with the destination node address D^ set to magnetic 5 and the source node address SA set to N113.

Microprocessor 20 then determines whether there are any remaining data frames to transmit in system memory 21 (step 516). If there is a remainder, an affirmative determination is made and the processing from step 515 (data frame transfer) onwards is repeated.

If there is no remaining frame and a negative determination is made, the dummy pattern generator 45 is activated again and the dummy frame is copied to the transmission buffer memory 38 (step 517).

Next, the microprocessor 20 controls the frame transmission control section 3.
6 (step 518), and the frame transmission control unit 36 sends a transmission instruction to the transmission buffer memory 38 in response to this instruction.
The frame stored in is read out and transmitted within LAN n (step 519). After the transmission is completed, the token is released (step 520).

By transmitting frames in this manner, as shown in FIG. 11, after transmitting one dummy frame and three data frames, one dummy frame is transmitted again.

Further, the operation when receiving and erasing the frame transmitted as described above will be described below.

First, the frame reception control unit 34 monitors whether a frame has been received. (Step 611) Then, when the reception control unit 34 detects that a dummy frame has been received, the frame reception control unit 34 notifies the microprocessor 21 that the dummy frame has been received (Step 612). The received frames have been copied to the receive buffer 35 via bus 41.42. When the MPU 20 is notified of the reception of the dummy frame and makes an affirmative determination, it determines whether the dummy flag in the system memory 21 is set to 1'' (step 615).

This dummy flag is a flag to indicate whether or not a dummy frame is received, and it becomes 1" every time a dummy frame is received.
Or it is changed to O''. Transmission buffer 3
At the time when the above-described series of frames (one dummy frame, three data frames, one dummy frame) are transferred from 8 onwards, the dummy flag is set to 0''.

Initially, since the dummy flag is set to 0'', a negative determination is made in step 615, and then the microprocessor 2
0, set the dummy flag to 1" (step 616)
, and then sends an instruction to erase the transmitted frame to the frame transmission control unit 36 (step 619).

In the frame transmission control 36, the received dummy frame is stripped in the same manner as in FIG. Thereafter, the process returns to step 611 and repeats the process.

Further, when the frame reception control unit 34 detects reception of a data frame, a negative determination is made in step 614 (whether the received frame is a dummy frame).

Next, the microprocessor 251 sets the dummy flag to 1".
If the determination is affirmative, the process from step 619 (frame deletion) is performed.

If three data frames are received after the first dummy frame, a positive determination is made in step 618 and the data frames are erased in step 619.

When the last dummy frame is received, an affirmative determination is made in step 614 (whether the received frame is a dummy frame), and an affirmative determination is made in step 615 (whether the dummy flag is 1'). Next, the microprocessor 251 sets the dummy flag to O'' (step 617), and then the frame is erased in step 619.

If a normal frame (a frame transferred between nodes other than node 1) is received, step 614. 6
Since both are negative in step 18, the received frame is not erased (therefore, it is transferred via the frame receiving unit 33, frame receiver 33, selector 39, and frame transmitting unit 40), and the processing from step 611 onward is repeated.

In this way, when a frame is transferred between networks via the bridge 1, dummy frames are transmitted before and after the data frame to be transferred. The microprocessor 20 monitors the frames received by the frame reception control unit 34, and erases one or more data frames sandwiched between two dummy frames.

〔Effect of the invention〕

As described above, according to the present invention, there is no need to change the format of a data frame to be transferred, and moreover, it is possible to transfer a plurality of data frames in succession. Furthermore, since it is not affected by changes in the number of nodes, etc., it is possible to flexibly respond to changes in the network configuration.

[Brief explanation of drawings]

FIG. 1 is a principle diagram of the present invention, FIG. 2 is a block diagram of a bridge according to the first embodiment of the present invention, and FIGS. 3 and 4 are:
FIG. 2 is an operation explanatory diagram, FIG. 5 is a block diagram of the bridge according to the second embodiment of the present invention, FIG. 6 is a frame format example of a dummy frame, and FIG. 7 is a frame diagram of the bridge in FIG. 5. 8 and 9 are flowcharts for explaining the operation of FIG. 5. FIG. 10 is a block diagram of the bridge of the third embodiment, FIG. 11 is a diagram for explaining the frame transmission procedure in the bridge of FIG. 10, and FIGS. 12 and 13 show the operation of FIG. 10. Flowchart for explanation; Figures 14 and 15 are system configuration diagrams targeted by the present invention; Figure 16 is a general frame configuration in a ring type LAN; Figure 17 is a diagram showing a conventional frame configuration between LANs. This is the frame format of the transfer frame.ゝ″2′−−Rooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so so sonum
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Claims (4)

[Claims] (1) An inter-network connection device that controls communication between local area networks including a ring local area network, with a node in the ring local area network as the destination and a node in another local area network as the source. Transmitting means for transmitting an inter-network transfer frame to the ring local area network following the dummy frame; detecting a dummy frame received from the ring local area network after transmitting the dummy frame; 1. An inter-network connection device comprising: removal means for removing the inter-network transfer frame received from the ring local area network. (2) The transmitting means transmits a second dummy frame to the ring local area network following the inter-network transfer frame, and the removing means sends a second dummy frame to the ring local area network after going around the ring local area network. Claim (1) characterized in that two dummy frames are detected, and inter-network transfer frames received between the first dummy frame and the second dummy frame are removed from the ring local area network. The network connection device described. (3) The transmitting means includes an identifying means for identifying the number of inter-network transfer frames to be transmitted after transmitting the dummy frame, and the removing means receives only the number specified by the identifying means subsequent to receiving the dummy frame. The inter-network connection device according to claim 1, wherein the inter-network transfer frame is removed. (4) An inter-network connection device that controls communication between local area networks including a ring local area network, with a node in the ring local area network as the destination and a node in another local area network as the source. transmitting means for storing the destination of an inter-network transfer frame to be sent to the ring-type local area network, and transmitting the destination of the inter-network transfer frame received from the ring-type local area network; An inter-network connection device comprising: removal means for removing the inter-network transfer frame from the ring local area network when the inter-network transfer frame matches.