JPH10215274A - Network connection device and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the signal transmission wait time of a transmitter by improving a throughput of the CSMA/CD communication system on a LAN network. SOLUTION: The network connection device is provided with a bridge function section 2 that bridges a signal between shared transmission lines 7, 8 by the CSMA/CD communication system and with a buffer circuit section 1 that selects direct passing of the signal between the shared transmission lines 7, 8 or interruption of the communication between the shared transmission lines 7, 8. Collision frequency measurement sections 61 , 62 measure collision frequency denoting a load state on the shared transmission lines 7, 8 and a passing packet monitor section 5 measures the number of packet signals passing through the bridge function section 2. A transmission line control section 3 compares the measured value with a reference value and switches the buffer circuit section 1 according to the comparison result to switch the buffer circuit section 1 and the bridge function section 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a CSMA / CD
(Carrier Sense Multiple A
access with Collision Dite
ction) communication LAN (Local Area)
network connection apparatus and method.

[0002]

2. Description of the Related Art As a transmission system for a LAN system in which transmission devices such as a plurality of workstations are connected to a shared transmission line, there is a CSMA / CD system. CSMA / CD
The transmission method means that the transmission apparatus detects a carrier signal (carrier) on a shared transmission path during transmission (Carrier Sense).
And data collision occurring on the shared transmission path
Is detected (Collision Detection), the signal transmission is stopped, and retransmission is performed after a certain delay time.

In general, in a LAN in which communication is performed in the CSMA / CD system, if communication is performed frequently, the shared transmission path becomes heavily loaded, and the occurrence of collisions increases.
The time during which the transmission device cannot transmit increases. Along with this, there is a problem that the throughput of the entire LAN is reduced and the response speed of the transmission device is reduced.

[0004] The above-mentioned decrease in throughput is likely to occur when the amount of data sent to the shared transmission path is large, and when the amount of data transmitted by one transmission device is constant, it is likely to occur as the number of transmission devices to transmit increases.

When a plurality of physically separated LANs are connected, if these are directly connected to form one shared transmission line,
The number of transmission devices connected to the shared transmission path increases compared to before connection, and the throughput decreases. In order to prevent this, a network connection device having a bridge function is inserted at a connection point of the shared transmission line of each LAN.

When a bridge receives a packet signal transmitted from one of the shared transmission lines connected thereto, the bridge transmits the packet signal to the other (output side) shared transmission line which is not the receiving side. Is transmitted in the CSMA / CD format.

When a collision occurs in the shared transmission line on the output side, the bridge temporarily stores the packet signal, waits until the collision does not occur, and then transmits the packet signal to the output side. As a result, even if a collision occurs in one of the shared transmission lines, it does not spread to the other side, and it is possible to suppress a decrease in throughput of the entire LAN.

The above-described bridge, which is generally used for connecting LANs, can also be used as a measure for improving the throughput of one LAN. That is, the shared transmission line of one LAN is divided into a plurality of sub-shared transmission lines,
If the plurality of divided sub-shared transmission paths are connected via the respective bridges, it is possible to improve the throughput when the shared transmission path of one LAN is in a high load state (the frequency of occurrence of collision is high). .

However, this method is rather disadvantageous when the shared transmission line is in a low load state (the frequency of occurrence of collision is low). This is because communication over two or more sub-shared transmission paths is always relayed and transmitted via a bridge, and the communication speed is reduced by the time required for relaying.

In order to solve this problem, Japanese Patent Laid-Open Publication No.
5633 divides the shared transmission line of one LAN into a plurality of shared transmission lines, measures the frequency of occurrence of collisions on each sub-shared transmission line, and determines between the shared transmission lines divided based on the measured frequency of occurrence of collision. A method for switching and inserting a bridge or a bypass transmission line for direct connection is disclosed.

FIG. 3 is a block diagram showing a configuration of a conventional network connection device disclosed in the above-mentioned publication. As shown in the figure, a conventional network connection device includes a bridge function unit 1, a bridge insertion switching unit 2, a collision frequency measurement unit 3, a bypass transmission line 4, and an A-system shared transmission line 5.
, A B-system shared transmission line 6, a transmission device 7, an A-system connection transmission line 8, and a B-system connection transmission line 9.

Next, the operation of the network connection device having this configuration will be described. First, it is assumed that the bridge function unit 1 is inserted between the A-system shared transmission line 5 and the B-system shared transmission line 6 via the A-system connection transmission line 8 and the B-system connection transmission line 9. The collision frequency measuring unit 3 measures the frequency of occurrence of collision in each of the A-system shared transmission line 5 and the B-system shared transmission line 6 in order to check the respective load states. Then, it is determined whether or not those measured values are equal to or less than a predetermined reference value.

When it is determined that the measured value is equal to or less than the reference value, the collision frequency measuring unit 3 sends a bypass instruction signal to the bridge insertion switching unit 2.

The bridge insertion switching unit 2 inserts the bypass transmission line 4 between the A-system shared transmission line 5 and the B-system shared transmission line 6 instead of the bridge function unit 1 based on the bypass instruction signal. Thus, the A-system shared transmission line 5 and the B-system shared transmission line 6 form one shared transmission line via the bypass transmission line 4, and the transmission device 7 on the A-system shared transmission line 5 and the B-system shared transmission line In communication with the transmission device 7 on the path 6, a higher communication speed can be obtained than when the bridge function unit 1 is inserted.

On the other hand, when the measured value of the collision frequency measuring unit 3 is larger than the reference value, the state where the bridge function unit 1 is inserted is maintained.

Even when the bypass transmission line 4 is inserted between the A-system shared transmission line 5 and the B-system shared transmission line 6, the collision frequency measuring unit 3 keeps the A-system shared transmission line 5 and the B-system shared transmission line The frequency of occurrence of collision 6 is measured. Then, it is determined whether or not the measured value is equal to or less than the reference value. If the collision frequency measurement is greater than the reference value,
The collision frequency measurement unit 3 sends a bridge insertion instruction signal to the bridge insertion switching unit 2.

The bridge insertion switching unit 2 replaces the bypass transmission line 4 between the A system shared transmission line 5 and the B system shared transmission line 6 based on the bridge insertion instruction signal received from the collision frequency measurement unit 3. The bridge function unit 1 is inserted via the shared transmission line 8 and the B-system shared transmission line 9. In this state, the transmission device 7 includes the A-system shared transmission line 5 and the B-system shared transmission line 6.
Distributed above. As a result, the number of transmission devices 7 per one shared transmission line is reduced as compared to before the bridge function unit 1 is inserted, and the frequency of occurrence of collision in each of the A-system shared transmission line 5 and the B-system shared transmission line 6 Decrease.

Therefore, the throughput in each of the A-system shared transmission line 5 and the B-system shared transmission line 6 is improved,
As a result, the throughput of the entire network including the A-system shared transmission line 5 and the B-system shared transmission line 6 is improved. At the same time, the communication speed between the transmission devices 7 connected to the A-system shared transmission line 5 and the communication speed between the transmission devices 7 connected to the B-system shared transmission line 6 are improved.

However, in the conventional network connection device described above, if there is a transmission device that frequently communicates between the transmission device on the A-system shared transmission line and the transmission device on the B-system shared transmission line, the bridge function unit 1 Works frequently each time.
However, since the bridge function unit 1 is also a single CSMA / CD transmission device, the operation of the bridge function unit 1 has the effect of increasing the frequency of occurrence of collisions on each shared transmission line, thereby improving the throughput. To diminish.

[0020]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to reduce the rate of occurrence of collision on a network and improve the throughput of the entire network. A network connection device and method are provided.

[0021]

To achieve the above object, a network connection device according to the present invention provides a CSMA / CD communication having a plurality of shared transmission lines including a first shared transmission line and a second shared transmission line. A network connection device that connects the first shared transmission line and the second shared transmission line of a system LAN, wherein the first shared transmission line and the second shared transmission line are connected to each other; A bridge function unit for transmitting a packet between the shared transmission line and the second shared transmission line, a passing packet monitoring unit for measuring the number of packet signals passing through the bridging function unit, and the passing packet monitoring unit When the measured number of passing packet signals is equal to or greater than a predetermined packet reference value, prohibits transmission between the first shared transmission path and the second shared transmission path via the bridge function unit, The first share And control means for disconnecting said second shared transmission path and transmission path, characterized in that it comprises a.

A collision frequency measuring unit for measuring a frequency of occurrence of collision of the first shared transmission line and a frequency of occurrence of collision of the second shared transmission line;
When the collision occurrence frequency measured by the collision frequency measurement unit is equal to or greater than a predetermined collision reference value, and the number of passing packet signals measured by the passing packet monitoring unit is equal to or greater than the reference value, the first shared transmission path and The second shared transmission path may be controlled so as to be separated from the second shared transmission path.

A collision frequency measuring unit for measuring a frequency of occurrence of collision between the first shared transmission line and the second shared transmission line, and a collision frequency measuring unit for measuring a collision frequency between the first shared transmission line and the second shared transmission line. And a bypass circuit that logically or physically connects the bypass circuit; and (1) when the collision occurrence frequency measured by the collision frequency measurement unit is less than a predetermined collision reference value, the bypass circuit Is connected between the first shared transmission line and the second shared transmission line to enable communication between the first shared transmission line and the second shared transmission line, and (2) When the collision occurrence frequency measured by the collision frequency measurement unit is equal to or greater than the collision reference value and the number of the passing packet signals measured by the passing packet monitoring unit is less than the packet reference value, the bridge function unit (3) connecting between the first shared transmission line and the second shared transmission line by connecting between the shared transmission line and the second shared transmission line; The first shared transmission line and the second shared transmission when the collision occurrence frequency measured by the unit is equal to or greater than the collision reference value and the number of passing packet signals measured by the passing packet monitoring unit is equal to or greater than the packet reference value. It may be configured to control so as to physically or logically separate the road.

[0024] For example, in a state where the bridge function unit is not connected to the first shared transmission line and the second shared transmission line, the control unit may detect the collision occurrence measured by the collision frequency measurement unit. Based on the frequency, the bypass circuit and the bridge function unit are connected to the first
And the second shared transmission line.

The bypass circuit comprises, for example, a bidirectional buffer.

[0026] Of the plurality of transmission devices connected to the first shared transmission line and the second shared transmission line, the transmission device that communicates most frequently with the first shared transmission line and the second shared transmission line. It is desirable to connect to either one of them.

Further, the invention according to the second aspect of the present invention provides a CSMA / CSMA transmission line access system in which a plurality of transmission devices sharing the shared transmission line are connected to the shared transmission line.
In a LAN network connection method using a CD system, a frequency of occurrence of collision on the shared transmission line is measured, and when the measured frequency of occurrence of collision is less than a first reference value, the first and second collisions are measured. A packet that bypasses the shared transmission path and connects the first and second shared transmission paths to each other via a bridge and passes the bridge when the measured collision frequency is equal to or greater than a first reference value. The number of signals is measured and the measured collision frequency is the first
The first and second shared transmission paths are separated when the number of packet signals passing through the bridge is equal to or more than the reference value and the number of packet signals passing through the bridge is equal to or more than the second reference value.

According to the above configuration, the first frequency is determined based on the collision occurrence frequency and / or the specified value of the number of passing packet signals.
Since the shared transmission line and the second shared transmission line are cut off, the frequency of occurrence of collision in each shared transmission line is reduced, and the network throughput can be improved. This can reduce the data retransmission waiting time of the transmission device.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A network connection device according to an embodiment of the present invention will be described below with reference to the drawings.

First, the configuration of the network connection device according to this embodiment will be described with reference to FIG. This network connection device includes a buffer circuit unit 1, a bridge function unit 2, a transmission line control unit 3, and transmission line switching units 4 ₁ , 4 ₂
And a passing packet monitoring unit 5 and a collision frequency measuring unit 6
_1, is composed of 6 ₂ which, with the A-system shared transmission channel 7 in which a plurality of transmission devices 9 ₁ is connected, and connects between the plurality of transmission devices 9 ₂ is connected B-based shared transmission path 8 I have.

The buffer circuit section 1 includes, for example, a bidirectional three-state buffers and the like, is connected between the transmission path switching 4 ₁ and 4 _2, A by switching command signal from the transmission path control unit 3 The system shared transmission line 7 and the system B shared transmission line 8 are connected (hereinafter referred to as opening the buffer) or cut off (hereinafter referred to as closing the buffer). The bridge function unit 2 is connected between the transmission line switching units 4 ₁ and 4 ₂ , and
And a packet signal from one side of the B-system shared transmission line 8 to the other side, and sends the packet signal to the other side in the CSMA system.

The transmission line control section 3 based on the collision frequency received from the number of collisions frequency measuring portion 6 ₁ and 6 ₂ of the traversing packet signal received from traversing packet monitoring unit 5, for setting the corresponding operating mode the switching command signal sent to the buffer circuit 1 and the transmission path switching 4 _1, 4 _2.

The transmission line switching units 4 ₁ and 4 ₂ are connected to the A system shared transmission line 7.
The buffer circuit unit 1 and the bridge function unit 2 are switched and connected between the B and the B-system shared transmission line 8. The passing packet monitoring unit 5 determines the number of packet signals passing from the A-system shared transmission line 7 to the B-system shared transmission line 8 and the number of packet signals passing from the B-system shared transmission line 8 to the A-system shared transmission line 7. Count the number. Then, the measurement result is converted into a signal and the transmission path control unit 3
Output to

The collision frequency measuring units 6 ₁ and 6 ₂ respectively measure the frequency of occurrence of collision in the A-system shared transmission line 7 and the B-system shared transmission line 8, and convert the measurement results into a signal to form a transmission line control unit 3.
Send to The A-system shared transmission line 7 is a first-system transmission line. The B-system shared transmission line 8 is a second-system transmission line. The transmission devices 9 ₁ and 9 ₂ include, for example, workstations connected to the A-system shared transmission line 7 and the B-system shared transmission line 8, respectively.

The operation of the network connection device will be described below. This network connection device has three operation modes: a bridge mode, a bypass mode, and a separate mode.

[0036] As shown in FIG. 2 (a), in the bridge mode, between the A-system shared transmission line 7 and the B-system shared transmission channel 8 is connected via a bridging unit 2, the transmission device 9 ₁ and the transmission CS communication between the device 9 ₂ via a bridging unit 2
It is relayed by the MA / CD communication system.

The bridge mode is used when one or both of the A-system shared transmission line 7 and the B-system shared transmission line 8 have a high collision occurrence frequency (high load state). In the bridge mode, the transmission devices 9 ₁ and 9 ₂ are dispersedly arranged on the A-system shared transmission line 7 and the B-system shared transmission line 8, and the number of units per system is reduced and the collision frequency is reduced. Further, even if one of the A and B2 systems connected by the bridge function unit 2 becomes extremely high-load, the high-load state does not spread to the other system, so that the throughput of the entire network is high.

As shown in FIG. 2B, in the bypass mode, the A-system shared transmission line 7 and the B-system shared transmission line 8 are directly connected by the open buffer circuit unit 1 to form one shared transmission line. ing. Communication between the transmission device 9 ₁ and the transmission device 9 ₂ is performed in a shared transmission path.

The bypass mode is used when the frequency of occurrence of collision in both the A-system shared transmission line 7 and the B-system shared transmission line 8 is low (low load state). In the bypass mode, since the relay communication by the bridge function unit 2 is not performed,
Compared to the bridge mode, there is no communication delay caused by the relay communication by the bridge function unit 2.

As shown in FIG. 2C, in the separate mode, the closed buffer circuit unit 1 is inserted between the A-system shared transmission line 7 and the B-system shared transmission line 8, and the A-system shared transmission line 7 is closed. Communication between the transmission path 7 and the B-system shared transmission path 8 is cut off, and independent transmission paths are formed. Transmission device 9
_1, 9 communication between the _two is performed independently on the A-system shared transmission channel 7 above or B based shared transmission path 8. Thus, communication between each other and the transmission device 9 ₂ connected to the transmission device 9 ₁ and B-system shared transmission path 8 connected to the A system shared transmission line 7 is interrupted.

[0041] When operating in the above bridge mode as the communication between the transmission device 9 ₁ and the transmission device 9 ₂ is performed through the bridging unit 2. However, bridging unit 2 similarly to the transmission device 9 ₁ and 9 _2, CSMA / CD
It is a type of transmission device that performs communication of the system. Therefore, if the number of transmissions from the bridge function unit 2 is too large, the frequency of occurrence of collision increases and the throughput decreases. In order to prevent this, the system A shared transmission line 7 and the system B shared transmission line 8 are separated,
By blocking the communication between the transmission device 9 ₂ connected to the transmission device 9 ₁ and B-system shared transmission path 8 connected to the A system shared transmission line 7, to improve the throughput as the entire network.

Hereinafter, the sequential operation will be described with reference to FIG. First, it is assumed that one of the buffer circuit unit 1 and the bridge function unit 2 is inserted and connected between the A-system shared transmission line 7 and the B-system shared transmission line 8. In order to check the respective load states of the A-system shared transmission line 7 and the B-system shared transmission line 8, the collision frequency measuring units 4 ₁ and 4 ₂ use the collision frequency measurement units 4 ₁ and 4 ₂ for the collision of Measure the frequency of occurrence. Then, the measured value is signalized and transmitted to the transmission path control unit 3. The A-system shared transmission line 7
In general, the frequency of occurrence of collision between the transmission line 8 and the B-system shared transmission line 8 has different values in the bridge mode and the separate mode. In the bypass mode, the values are the same since they are logically one shared transmission line.

On the other hand, the passing packet monitoring unit 5 determines the number of packet signals passing through the bridge function unit 2 from the A-system shared transmission line 7 to the B-system shared transmission line 8 (the number per unit time).
The number of packet signals passing from the B-system shared transmission line 8 to the A-system shared transmission line 7 is measured, and the value is signalized and transmitted to the transmission line control unit 3. When the number of passing packet signal is large, the bridge mode, the frequent communication between the transmission device 9 ₂ connected to the transmission device 9 ₁ and B-system shared transmission path 8 connected to the A system shared transmission channel 7 There is a transmission device that performs the communication, and communication via the bridge function unit 2 is frequently performed, and the frequency of occurrence of collision is increased by this communication.

The transmission line control unit 3 includes a collision frequency measurement unit 6
_1, determines from the signal sent from the 6 _2, whether a collision occurrence frequency is the reference value (collision reference value) or more. In addition, it is determined whether or not the number of passing packet signals is equal to or more than a reference value (packet reference value) from the signal transmitted from the passing packet monitoring unit 5. The transmission line control unit 3 connects the bridge function unit 2 between the A-system shared transmission line 7 and the B-system shared transmission line 8 (bridge mode) or sets the opened buffer circuit unit 1 in accordance with the combination of the determination results. either connect (bypass mode), closed Baffua connect the circuit (separate mode) by selecting a command signal corresponding to the operation mode to the buffer circuit 1 and the transmission path switching 4 _1, 4 _2, below Is transmitted based on the selection criterion.

Next, the operation mode selection criteria will be described. Here, the collision occurrence frequency of the A-system shared transmission line 7 is abbreviated as the A-system collision frequency, and the collision occurrence frequency of the B-system shared transmission line 8 is abbreviated as the B-system collision frequency. If the value equal to or higher than the reference value is expressed as “high”, the collision frequency for these combinations is determined as shown in Table 1.

[0046]

[Table 1] A system collision frequency low B system collision frequency low → collision frequency low A system collision frequency low B system collision frequency high → collision frequency high A system collision frequency high B system collision frequency low → collision frequency high A system collision frequency High B-system collision frequency high → collision frequency high

Depending on the level of the collision frequency and whether the number of passing packet signals is equal to or greater than the reference value, 4
Can be combined. Table 2 for each combination
, Three operation modes are assigned.

[0048]

[Table 2] Collision frequency low and number of passing packet signals → bypass mode Collision frequency low and number of passing packet signals → bypass mode collision frequency high and number of passing packet signals → bridge mode collision frequency high and number of passing packet signals → Separate mode

After the operation mode is once set to the separate mode, the A-system shared transmission line 7 and the B-system shared transmission line 8
Is disconnected and communication becomes impossible. In this case, the number of passing packet signals becomes zero. Therefore, if the mode assignment condition in Table 2 is applied as it is, the separate mode immediately shifts to the bypass mode or the bridge mode. Therefore, in the bypass mode, the transmission path control unit 3 ignores the number of passing packet signals, pays attention only to the frequency of occurrence of collision, and shifts to the bypass mode when the frequency of collision decreases.

For example, it is assumed that the system is in the bypass mode and the A-system shared transmission line 7 and the B-system shared transmission line 8 are connected by the buffer circuit unit 1. In this state, _second transmission device 9 ₁ and 9 are substantially connected via a single shared transmission path between transmission devices 9 ₁ mutually between the transmission device 9 ₂ mutually transfer device 9 ₁ perform appropriate communication between 9 _2. In this state, for example, the number of collisions per unit collision frequency measuring portion 6 ₁ and 6 ₂ are measured time is equal to or greater than the reference value. At this time, the bridge function unit 2
Since it is not connected between the shared transmission lines 7 and 8, the number of passing packet signals becomes zero. The passing packet monitoring unit 5
It counts 0 and notifies the transmission path control unit 3.

The transmission path control unit 3 determines from the count values of the collision frequency measurement units 6 ₁ and 6 ₂ that the collision frequency is higher than the reference value and the number of passing packet signals is smaller than the reference value. From Table 2, the selection of the bridge mode is selected. This selection transmission line control unit 3 sends a switching instruction signal to the bridge mode to the transmission path switching 4 ₁ and 4 _2. Transmission path switching section 4 ₁ and 4 _2, cut off the connection between the shared transmission channel 7, 8 and the buffer circuit section 1, alternatively, 2
As shown in (a), the bridge function unit 2 is connected.

[0052] In this state, the transmission device 9 ₁ communicate with each other via the A-system shared transmission channel 7. In addition, the transmission device 9 ₂
Communicate with each other via the B-system shared transmission line 8. Further, the transmission devices 9 ₁ and 9 ₂ communicate with each other via the bridge function unit 2.

Here, when the collision frequency is reduced by connecting the bridge function unit 2, the transmission path control unit 3
Detects this from the output signal of the collision frequency measuring portion 6 ₁ and 6 _2, and outputs the bypass switching command to the transmission path switching 4 ₁ and 4 _2. Transmission path switching section 4 ₁ and 4 ₂ in accordance with this signal, instead of the bridging unit 2 connected between the buffer circuit 1 of the A-system shared transmission line 7 and the B-system shared transmission path 8. Further, the transmission path control unit 3 transmits a buffer open signal to the buffer circuit unit 1 to open the buffer. As a result, the bypass mode is set, and the A-system shared transmission line 7 and the B-system shared transmission line 8 function as one shared transmission line.

On the other hand, after reaching a bridge mode is also a high collision frequency notified from the collision frequency measuring unit 6 ₁ and 6 _2, moreover if the number of passing packet signal is notified from the passing packet monitor 5 is large , Transmission path control unit 3
Connects the buffer circuit unit 1 instead of the bridge function unit 2 between the A-system shared transmission line 7 and the B-system shared transmission line 8 to set the separate mode. Further, a buffer close signal is transmitted to the buffer circuit unit 1 to close the buffer. Thereby, the A-system shared transmission line 7 and the B-system shared transmission line 8
And is separated.

In the separate mode, the transmission path control unit 3 determines the operation mode based only on the collision frequency without considering the number of passing packet signals notified from the passing packet monitoring unit 5. For example, if the collision frequency is low, the bypass mode is set, and if the collision frequency is high, the separate mode is maintained.

[0056] In this way, the transmission path control unit 3, based on the current operation mode, data on the A and B systems shared transmission line 7 and 8 which are notified from the collision frequency measuring portion 6 ₁ and 6 ₂ One of the modes is set based on the frequency of collision and the number of packet signals passing through the bridge 2 notified from the passing packet monitoring unit 5. Therefore, an optimal mode is set, and high-speed transmission by the transmission devices 9 ₁ and 9 ₂ becomes possible. The transmitted data may be destroyed immediately after the opening and closing of the buffer circuit section 1 and the like. In this case, the data can be dealt with by retransmitting the data.

In the configuration shown in FIG. 1, a specific transmission device that frequently communicates on a network (for example, two workstations that frequently communicate with each other) may be known in advance. In such a case, it is desirable to connect these transmission devices intensively to one system, for example, the shared transmission line 7 of the A system. With such a connection, the specific transmission devices are always in a direct communication state, and the communication speed between the specific transmission devices can be increased. Further, the frequency of communication via the bridge function unit 2 can be reduced, and the load on the B system is relatively reduced, and as a result, the throughput of the entire network is improved.

The determination algorithm for switching the operation mode is not limited to those shown in Tables 1 and 2. For example, if the reference value is fixed, the bypass mode and the bridge mode may be frequently switched. In such a case, the reference value when shifting from the bypass mode to the bridge mode and the reference value when shifting from the bridge mode to the bypass mode may be set to different values (hysteresis is given to the mode change). In addition, a certain operation mode may be maintained for a predetermined time or more, and after the predetermined time has elapsed, the operation mode may be switched or maintained based on the frequency of collision occurrence and / or the number of passing packet signals.

Further, if the operation mode is switched while communication is being performed via the connection device of this embodiment, there is a possibility that the signal being communicated may be destroyed. In response to this, the open / closed state of the buffer of the buffer circuit unit 1 may be notified to each of the transmission devices 9 ₁ and 9 ₂ . Or it may be retransmitted as usual.

[0060]

According to the present invention, the frequency of occurrence of collision in one or both of the first shared transmission line and the second shared transmission line, and / or from the first shared transmission line to the second shared transmission line. Alternatively, the first shared transmission path and the second shared transmission path are separated (communication is cut off) based on the number of packet signals passing from the second shared transmission path toward the first shared transmission path. Collision occurrence frequency of each shared transmission line decreases,
Network throughput can be improved.
This can reduce the data retransmission waiting time of the transmission device.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a network connection device according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining an operation mode of the network connection device according to the embodiment of the present invention;

FIG. 3 is a block diagram showing a configuration of a conventional network connection device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Buffer circuit part 2 Bridge function part 3 Transmission line control part 5 Passing packet monitoring part 7 A system common transmission line 8 B system common transmission line 4 ₁ Transmission line switching part 4 ₂ Transmission line switching part 6 ₁ Collision frequency measurement part 6 ₂ Collision frequency measurement unit 9 ₁ transmission device 9 ₂ transmission device

Claims (7)

[Claims] 1. A first and a second shared transmission line of a CSMA / CD communication system LAN having a plurality of shared transmission lines including a first shared transmission line and a second shared transmission line. A network connection device for connecting the first shared transmission line and the second shared transmission line, and transmitting a packet between the first shared transmission line and the second shared transmission line. A bridge function unit, a passing packet monitoring unit that measures the number of packet signals passing through the bridge function unit, and when the number of passing packet signals measured by the passing packet monitoring unit is equal to or greater than a predetermined packet reference value, Prohibiting transmission between the first shared transmission line and the second shared transmission line via the bridge function unit, and substantially eliminating the first shared transmission line and the second shared transmission line. Control means for disconnecting; Network connection apparatus according to claim. 2. The apparatus according to claim 1, further comprising: a collision frequency measuring unit configured to measure a collision occurrence frequency of the first shared transmission line and a collision occurrence frequency of the second shared transmission line. When the collision occurrence frequency measured by the above is equal to or more than a predetermined collision reference value and the number of passing packet signals measured by the passing packet monitoring unit is equal to or more than the packet reference value, the first
2. The network connection device according to claim 1, wherein control is performed such that the shared transmission line is separated from the second shared transmission line. 3. A collision frequency measuring section for measuring a frequency of occurrence of collision between the first shared transmission line and the second shared transmission line, and a first and second shared transmission line. And a bypass circuit that connects between the first shared circuit and the first shared circuit when the collision occurrence frequency measured by the collision frequency measurement unit is less than a predetermined collision reference value. Connected between a transmission line and the second shared transmission line to enable communication between the first shared transmission line and the second shared transmission line,
(2) When the collision occurrence frequency measured by the collision frequency measurement unit is equal to or greater than the collision reference value, and the number of the passing packet signals measured by the passing packet monitoring unit is less than the packet reference value, the bridge function unit (3) connecting between the first shared transmission line and the second shared transmission line to enable communication between the first shared transmission line and the second shared transmission line; When the collision occurrence frequency measured by the collision frequency measuring unit is equal to or more than the collision reference value and the number of passing packet signals measured by the passing packet monitoring unit is equal to or more than the packet reference value, the first shared transmission path and the second The network connection device according to claim 1, wherein the shared transmission line is physically or logically separated. 4. The apparatus according to claim 1, wherein the control unit is configured to, when the bridge function unit is not connected to the first shared transmission line and the second shared transmission line, detect a collision occurrence measured by the collision frequency measurement unit. The network connection device according to claim 3, wherein the bypass circuit and the bridge function unit are connected between the first shared transmission line and the second shared transmission line based on a frequency. . 5. The network connection device according to claim 3, wherein the bypass circuit includes a bidirectional buffer. 6. A transmission device that communicates most frequently among a plurality of transmission devices connected to the first shared transmission line and the second shared transmission line is the first shared transmission line and the second shared transmission line. The network connection device according to any one of claims 1 to 5, wherein the network connection device is connected to one of the transmission lines in a concentrated manner. 7. A network connection method for a LAN in which a CSMA / CD system is used as a transmission line access method in which a plurality of transmission devices sharing the shared transmission line are connected to the shared transmission line, wherein: A collision occurrence frequency is measured, and when the measured collision occurrence frequency is less than a first reference value, the first and second shared transmission lines are mutually bypassed, and the measured collision frequency is set to a first reference value. In these cases,
The first and second shared transmission paths are connected to each other via a bridge, and the number of packet signals passing through the bridge is measured. When the measured collision frequency is equal to or higher than a first reference value, the signal passes through the bridge. Separating the first and second shared transmission lines when the number of packet signals to be transmitted is equal to or greater than a second reference value.