JPH0918507A - Repeating device - Google Patents

Abstract

PURPOSE: To reduce transmission delay and suppress an error frame by providing two operation modes which correspond to an on-the-fly device and a store-and- forward device and automatically switching them according to the error state of a frame. CONSTITUTION: A mode switching control circuit 12 control in which mode a repeating circuit 13 corresponding to each port is by setting a flag in a state register 122. In an initial state, an on-the-fly mode is set in the repeating circuits 13 of all ports. Further, the mode switching control circuit 12 has a port counter 123 and counts the numbers of error frames and normal frames, port by port. If an error occurs successively >=3 times in the on-the-fly mode, the repeating circuit 13 is set in stored-and-forward mode. When a no-error state succeeds >=3 times in the store-and-forward mode, the repeating circuit 13 is put back to the original on-the-fly mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay device, and more specifically, to a terminal or a transmission line in a LAN transmission line relay device in which terminal devices (hereinafter, terminals) connected to a LAN share the same transmission line. 1 frame (1 unit telegram information) from the terminal is distributed to each connected terminal, or the 1 frame telegram is transmitted to the transmission line.
The present invention relates to a relay device capable of selecting an optimum transmission form according to the occurrence state of an error frame.

[0002]

2. Description of the Related Art All LANs connected to the same relay device
LAN in which the terminal adopts a CSMA / CD (Carrier Sense Multiple Access With Collision Detection) control device (IEEE802.3 MAC (Media Access Control) control device) that shares the same transmission path Conventionally, there are the following two relay devices. (1) On-the-fly type relay device (hereinafter, on-the-fly device) (2) Store-and-forward type relay device (hereinafter, store-and-forward device) The on-the-fly device Starts relaying the received frame to the destination port when the destination MAC address 4 of the header portion at the head of the received frame 1 shown in FIG. 3 is received. Therefore, there is an advantage that the transmission delay (time for holding the received frame inside the device) is constant and is very small. However, this has the drawback of relaying error frames as well, since no error checking is done.
In frame 1, 2 is the preamble, 3 is
SFD (start frame delimiter), 4 is destination MAC
Address 5 is a transmission MAC address, 6 is a type, a protocol number or a byte length of a message, 7 is transmission data, and 8 is a CRC check code.

The store-and-forward device described above is
An error check is performed after temporarily storing all the received frames for one frame in the memory, and only normal frames are relayed to the destination port. Therefore, the transmission delay increases in proportion to the frame length. However, since the error frame transmission is suppressed, the use time of the transmission path is eliminated. A conventional relay device generally has one of these two relay devices. Also, in the case of having both relay devices, one of them is selected by an input operation from the outside to switch the relay device.

[0004]

When handling moving image data, it is preferable that frames are continuously transmitted at high speed. In this relationship, an on-the-fly device with a small transmission delay is effective, but due to the relationship of receiving and relaying an error frame, the device is occupied for a lot of unnecessary relay due to the error frame, and the throughput is reduced. There's a problem. Therefore, in general, store and store that can suppress error frames and does not affect other networks.
Although a forward device is used, a transmission delay of one frame becomes a problem due to an increase in transmission of moving image data as multimedia that integrates moving images, voices, text data, and the like becomes widespread.

It is also conceivable that two relay devices are provided in advance depending on the form and usage of the transmission path and these are switched so that the limited transmission path can be used more efficiently. Since it is necessary to monitor the state of the transmission line and switch manually, it is troublesome and there is a problem that proper switching cannot be performed from the viewpoint of other terminals due to the fact that the devices individually switch. An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a relay device having a small transmission delay and suppressing an error frame.

[0006]

The features of the relay apparatus of the present invention for achieving such an object are that a memory for storing received frame data and a received frame data stored in this memory are provided. An error check circuit that performs an error check, a counter that counts the determination result of this error check circuit, and when the destination address in the received frame is received or the header part including this destination address is received, this destination address is The first operation mode for sending the data of the received frame to the port of the destination address when it is an address managed by the Destination address when is the address of the port managed by The port has a second operation mode for sending the data of the received frame to the transmission path otherwise, and a relay circuit set to either operation mode according to the control signal, and the relay circuit has a first operation mode. When the operation mode is set to, the count result of the error is counted by the counter, and the control signal for setting the relay circuit to the second operation mode is transmitted to the relay circuit when the error determination result occurs a plurality of times continuously, When the relay circuit is set to the second operation mode, the counter counts the determination result when there is no error, and when it occurs a plurality of times continuously, a control signal for setting the relay circuit to the first operation mode is output. And a control circuit for sending to a relay circuit.

[0007]

As described above, two modes, the first operation mode corresponding to the on-the-fly apparatus and the second operation mode corresponding to the store-and-forward apparatus, are provided to respond to the error state of the frame. These are automatically switched, and the frame is received at the time when the header part of the received frame received from the terminal or the transmission line or the destination address thereof is received, or when the whole one frame is received. In the first mode operation as an on-the-fly apparatus, the relay of the frame to the destination port or the bus is started simultaneously with the detection of the received frame without performing the error check, and the store and -When operating in the second mode as the forward device, an error check is performed at the same time when the reception of one frame is completed and the destination port Stomach so as to relay only the normal frame to the bus. Furthermore, in order to automatically switch between the on-the-fly device operation and the store-and-forward device operation for each port, the received frame is monitored for errors. When the error check circuit determines that an error frame has been received while operating as an on-the-fly device, the counter counts up the error frame, and the error frame continues counting. When the number reaches a predetermined number, the mode is switched to the other mode to operate in the store-and-forward mode.

On the other hand, in a port operating as a store-and-forward device, a normal frame (frame determined to have no error) by an error check circuit
When it is determined that the frame has been received, the frame is counted up, and when the number of consecutive frames reaches a predetermined number, the mode is switched to the other mode and the on-the-fly mode To work. In this way, while monitoring the received frame for errors, the relay mode currently operating and the error or error-free state are detected as a condition for switching it, and the mode is automatically selected as appropriate. By switching to the other side, it automatically turns on / off according to the error state of the received frame.
The operation as the fly device and the operation as the store-and-forward device are selected. This enables on-the-fly device operation in normal frames, and basically, as long as the error does not continue, the operation as the on-the-fly device basically integrates video, audio, and text data. It is possible to perform a relay suitable for information transmission of media. In addition, if such relaying is performed for each port, the mode can be switched for each port instead of for the entire device. Therefore, the transmission content (traffic) of the frame received from the terminal or the transmission path can be changed. The corresponding relay can be done at each port. Further, according to the present invention, the device automatically switches the relay mode without performing an input operation from the outside, so that the input operation related thereto can be eliminated.

[0009]

1 is a block diagram of an embodiment of a relay device to which the present invention is applied, and FIG. 2 is a flow chart of a mode switching process. Reference numeral 10 is a relay device, and 11 is a port for transmitting a received frame received from a terminal or a transmission line to which the relay device 10 is connected to a destination port or a transmission line and a destination port or transmission line. It is a changeover switch unit that is selectively connected to form a passage. It consists of a so-called multi-port bridge circuit. Reference numeral 12 is a mode switching control circuit for controlling error frame monitoring and relay switching, and 13a, 13b, ...
13n is a relay circuit, and is a relay circuit 13a, 13
b, ..., 13n are mode controls each having an on-the-fly mode for relaying as an on-the-fly device operation and a store-and-forward mode for relaying as a store-and-forward device operation. Part 130,
The bidirectional transmission circuit 133 includes a memory 131 that stores data for one received frame, an error check circuit 132, a bidirectional transmission circuit 133, and a port table 134 that searches a port corresponding to this address from a destination address. It is connected to the changeover switch unit 11 and the bus 14.

The relay circuits 13a, 13b, ..., 13n (hereinafter, these are representatively described as the relay circuit 13) are provided corresponding to the respective ports 1 to n, and are connected to the LAN-connected bus 14. ing. Then, each relay circuit 13
Refers to the port table 134 to receive data (received frame) from the terminals connected to the respective ports to the other port connected to the relay device 10 when the destination, and otherwise, It is sent to the bus 14 via the changeover switch unit 11. The mode control unit 130 of each relay circuit 13 is composed of a gate array or an MCU, and when receiving data from a terminal connected to its port or the bus 14, the memory 1
When it is stored in 31 and the on-the-fly mode setting signal is received from the mode switching control circuit 12, the relay circuit 13 is set to the on-the-fly mode operation,
When the destination address 4 is received, the port table 134 is referred to obtain the destination port corresponding to the contents of the destination address 4, and the changeover switch unit 11 is connected to the destination port or the destination port is connected. When not present, a control signal for switching the connection is sent to the bus 14.

When the store-and-forward mode setting signal is received from the mode switching control circuit 12, the relay circuit 13 is set to the store-and-forward mode operation and the error check result of the error check circuit 132 is obtained. Control that refers to the port table 134 according to the destination address 4 received only when it is determined that there is no error in the received data, and changes the connection to the changeover switch unit 11 corresponding to the destination port or to the bus 14. Send a signal. And in this mode,
When there is an error, the received data is not transferred. The mode control unit 130 switches from another port to the changeover switch unit 1
When the received data is transferred via 1, the received data is transferred to the terminal connected to its own port via the bidirectional transmission circuit 133 and the data is dropped to the terminal. Further, the error check result of the error check circuit 132 for the received data and one frame is sent to the mode switching control circuit 12 with its own port code.

The mode switching control circuit 12 includes an MPU 120.
And a memory 121, a status register 122, and a port counter 123.
Is a counter provided for each port that counts the number of error frames and normal frames for each port. For example, a soft counter that stores the count value of each port in a predetermined area of memory. It is composed of. Each of these counters is a ternary counter that generates a count-up signal when it exceeds 3. The mode switching control circuit 12 manages the mode state by setting a flag in the state register 122 indicating which mode the relay circuit 13 corresponding to each port is in. For example, in store-and-forward mode, the flag at the position corresponding to that port is set to "1", and in the on-the-fly mode, the flag at the position corresponding to that port is reset to "0". To be done.

The mode switching control circuit 12 executes the mode switching processing by executing the mode switching program 121a stored in the memory 121 by the MPU 120 according to the flowchart of FIG. That is, in FIG. 2, first, each counter of the state register 122 and the port counter 123 is reset (step 100), and in the initial state,
A signal for setting the on-the-fly mode is sent to the relay circuits 13 of all ports (step 101). Then, an interrupt waiting loop for whether or not there is an error check interrupt is entered, and the error check result of the error check circuit 132 of each relay circuit 13 is received (step 1
02), when YES, the state register 120 is referred to judge whether the mode is the on-the-fly mode or the store-and-forward mode (step 103). Then, in the on-the-fly mode, it is determined whether or not the determination result is an error (step 104), and when an error is detected, the counter of the port corresponding to the received relay circuit 13 of the port counter 15 (relay circuit The counter associated with the port code sent from 13 together with the error result) is incremented (step 105), it is determined whether the value of the counter is 3 (step 106), and when it is 3 (YES). Sometimes, the store-and-forward mode setting signal is sent to the relay circuit 13 of the port corresponding to this counter, and the status register 122 is set to "1" (step 107). When it is determined in step 106 that the counter value is not 3 or more, the process returns to step 102. Then, if it is determined in step 104 that there is no error, the counter value of the port corresponding to the received relay circuit 13 is reset (to "0").
Then (step 108), the process returns to step 102. This will turn on unless an error occurs three times in a row.
Try to keep the fly mode.

On the other hand, when the store-and-forward mode is determined in the determination in step 103, it is determined whether or not the determination result is an error (step 109), and when it is not an error, it corresponds to the relay circuit 13 received by the port counter 15. Incrementing the counter of the port (the counter associated with the port code sent from the relay circuit 13 together with the error result) (step 110),
It is determined whether or not the value of the counter is 3 or more (step 111), and when it is 3 or more (when YES),
The on-the-fly mode setting signal is sent to the relay circuit 13 of the port corresponding to this counter, and the status register 122
Is reset (to "0") (step 112). When it is determined in step 111 that the counter value is not 3 or more, the process returns to step 102. Then, if an error is found in the determination in step 109, the value of the counter of the received port corresponding to the relay circuit 13 is reset (step 108) and the process returns to step 102. As a result, the store-and-forward mode is maintained unless the error-free state continues three times.

As a result, first, the relay circuit 13 is turned on.
For example, when the destination address is received from the terminal for the transfer data of one frame received through the port 1 while operating in the fly mode, another port or bus is operated through the changeover switch unit 11. Transfer to 14. Similarly, the data received from the bus 14 is transferred to the terminal connected thereto via the port 1 when the destination is the self.

When an error occurs three times or more in the received frame in the on-the-fly mode, the relay circuit 13 is set to the store-and-forward mode and is received from the terminal via the port 1, for example. When one frame of data is stored in the memory 131 with respect to the transferred one frame of transferred data and the result is not an error according to the determination result of the error check circuit 132, the changeover switch is selected according to the received destination address. Part 11
To the other port or the bus 14 via. If the result is an error, the transfer is aborted. Similarly, regarding the data received from the bus 14, when the result is not an error according to the determination result of the error check circuit 132, and when the received destination is the self, the port 1
To the terminal connected to this via. If the result is an error, the transfer is aborted.

In this way, when the error occurs three times or more continuously in the on-the-fly mode, the relay circuit 13 is set to the store-and-forward mode, and the store-and-forward mode is set. When the error-free state occurs three times or more consecutively, the relay circuit 13 is returned to the original on-the-fly mode, and the transmission data is relayed based on the on-the-fly mode.

As described above, the mode control unit 130
May have a built-in MPU and operate in accordance with a program similarly to the mode switching control circuit 12. Also,
On the contrary, the mode switching control circuit 12 may be configured by a logic circuit such as a gate array instead of being operated by a program. Further, in the embodiment, the continuous count number of errors or the continuous count number of non-errors is set to 3 or more, but the determination may be 3 or not. Further, this may be repeated a plurality of times, and the numerical value is not limited to 3.

[0019]

As described above, according to the present invention, since it operates as an on-the-fly device, it is possible to transmit a frame with a very small delay, and when an error frame occurs, automatic transmission is possible. Since it is switched to operate as a store-and-forward device, the error frame for the destination port can be suppressed and the relay device of another port is not affected. Also, when a normal frame is received from a port that has been switched to store and forward operation, it automatically recovers to operation as an on-the-fly device, so an error frame occurs for each port. It can operate with the most suitable relay device according to the situation. Further, since the switching of these relay devices is automatically performed by the device, there is an effect that an input operation from the outside can be eliminated.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a relay device to which the present invention is applied. Fig. 1

FIG. 2 is a flowchart of a mode switching process.

FIG. 3 is an explanatory diagram of a frame format of IEEE802.3.

[Explanation of symbols]

10 ... Relay device, 11 ... Changeover switch section, 12 ... Mode change control circuit, 13, 13a, 13b, ..., 13n ... Repeater circuit, 14 ... Bus, 120 ... MPU, 121 ... Memory, 122 ... Status register, 123 ... Port counter,
130 ... Mode control unit, 131 ... Memory, 132 ... Error check circuit, 133 ... Bidirectional transmission circuit, 134 ... Port table.

Claims (2)

[Claims] 1. A memory for storing received frame data, an error check circuit for performing an error check on the received frame data stored in the memory, and a counter for counting the determination result of the error check circuit. At the time of receiving the destination address in the received frame or at the time of receiving the header part including this destination address, when this destination address is an address managed by itself, it is transmitted to the port of the destination address, otherwise it is transmitted. When the destination address is the address of the port managed by itself when the determination result of the error check circuit is not an error in the first operation mode for transmitting the data of the received frame to the route, the port of the destination address is set. , If not, the reception frame on the transmission line A relay circuit having a second operation mode for transmitting data of a system, the relay circuit being set to one of the operation modes according to a control signal, and the relay circuit being set to the first operation mode. Occasionally, the counter counts an error determination result, and when the error determination result occurs a plurality of times consecutively, the control signal for setting the relay circuit to the second operation mode is sent to the relay circuit, When the second operation mode is set, the counter counts the determination result when there is no error, and when the occurrence occurs continuously a plurality of times, the relay circuit is set to the first operation mode And a control circuit for sending a signal to the relay circuit. 2. A switch unit capable of switching connection corresponding to each of a plurality of ports, wherein the relay circuit controls switching of the switch unit to a port of the destination address or the transmission line. The relay device according to claim 1, wherein the reception frame is transmitted.