JP3152039B2 - LAN connection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a LAN connecting device for connecting a plurality of terminals to form a network, and more particularly to a LAN connecting device capable of reducing frame collision.

[0002]

2. Description of the Related Art As a standard of a star network, IEEE802.3 defined by the Institute of Electrical and Electronics Engineers, IEEE.
10BASE-T is widely known. The relay device defined in this standard includes a plurality of input ports and a plurality of output ports that are paired with the input ports, and relays frames between these input / output ports. FIG. 5 shows a configuration example of a star network using this relay device. This star type network includes a relay device 301, a plurality of terminals 302a, 302b, 302c, 302d, and bidirectional links 303a, 303b, 303c,
303d. Each terminal is a relay device 30
1 can exchange frames with one another.

FIG. 6 shows an example of the configuration of a star network in which more terminals are connected to a plurality of relay devices. By using a plurality of relay devices, it is possible to flexibly cope with an increase in the number of terminals. In this configuration example, one port of the relay device 401c is connected to the preceding relay device 401b, and one port of the relay device 401b is further connected to the preceding relay device 401a. Then, for example, a frame can be relayed between many terminals such that the terminal 402a and the terminal 403a are relayed via the relay device 401a and the relay device 401b.

[0004] Further, as shown in FIG.
2.3 A transmission line 505 conforming to 10BASE5 or 10BASE2 is used as a trunk, and a relay device 501 is connected to this trunk.
a, 501b and 501c are also connected.

[0005] Each of the relay devices used in the configuration examples shown in FIG. 3, FIG. 4 or FIG. 5 has the following features.

(1) When a frame arrives at any input port, if there is no other relay frame in the relay device, the relay device immediately relays the frame.

(2) A frame arriving at a certain input port is not relayed to an output port paired with this input port. In other words, the relay device performs selective relay such that the frame is not sent back to the source of the frame.

(3) When a frame arrives at any of the input ports and there is a frame currently being relayed, the relay of the currently relayed frame and the relay of the arrived frame both fail. At this time, the relay device stops the relay, transmits a signal called “jam” to all the ports, and notifies the relay that the relay has failed. Such a situation is called a "(frame) collision".

Further, each terminal performs communication having the following features according to the communication control system defined in the above standard.

(1) The length of a frame is limited.

(2) When a frame transmission request is generated at a terminal, the terminal detects its own reception port, confirms that there is no transmission frame from another terminal over a predetermined interval, and immediately transmits the frame. Send. When there is a transmission frame from another terminal, the transmission frame ends, and after confirming that there is no transmission frame from another terminal for a certain interval or more, the frame transmission is performed.

(3) The terminal detects the receiving port even during the frame transmission while the transmission condition of (2) is satisfied.

(4) If a transmission frame is detected at the reception port during frame transmission, it is determined that a frame collision has occurred, and a jam is transmitted.

(5) When transmission of a frame fails, the terminal attempts retransmission after a predetermined time has elapsed.

[0015]

[Problems to be Solved by the Invention] IEEE802.3
A network using a relay device based on the 10BASE-T standard has the following problems.

That is, when there is a frame collision, the transmission of the currently transmitted frame and the transmission of the subsequently transmitted frame both fail. Since both frames will be retransmitted, the traffic will increase accordingly. As frame collisions increase, traffic further increases and frame arrival delays increase dramatically.

The above phenomenon becomes remarkable especially when a large number of terminals are connected in the network configuration as shown in FIGS.

It is an object of the present invention to solve the above-mentioned problems and to provide a LAN connection device capable of reducing frame collision.

[0019]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a LAN connection device having a plurality of input / output ports and a repeater, and relaying a frame between the input / output ports by the repeater. At least one input / output port is connected to a trunk line, a source address detector for detecting a source address from a frame arriving at each input / output port, and a destination address detector for detecting a destination address from a frame to be relayed And when the destination address matches any of the transmission source addresses detected at the input / output ports, a control unit is provided to prevent the trunk input / output port from relaying.

The source address detector may be connected to each input / output port side of the repeater, and may detect a source address from a frame arriving for each input / output port.

The source address detector may be connected to the trunk of the repeater, and the repeater may detect the source address from a frame to be relayed to the trunk.

A source address detector and a destination address detector for detecting a source address and a destination address of an arriving frame are provided at each of the plurality of input / output ports, and the source addresses correspond to the input / output ports. And an address search unit for searching for an input / output port in which a source address matching the destination address is registered, and a first trunk line is extracted from each input / output port, and the first trunk line is connected to the first trunk line. A plurality of second relay lines are bridged through the respective relay switches, and the first relay line of the input / output port where the frame has arrived and the first relay line of the searched input / output port are connected to the second relay line. A control unit for closing the relay switch so as to short-circuit the line is provided.

If the address search unit cannot search for the corresponding input / output port, the control unit may close the relay switches of all the input / output ports.

When the arrival frame is a broadcast frame, the control unit may close the relay switches of all the input / output ports.

[0025]

According to the above configuration, the source address detector of the LAN connection device detects the source address from the frame arriving at each input / output port. Since the source address is the address of the terminal that transmitted the frame to the input / output port, the terminal connected to the input / output port of the LAN connection device is recognized. The destination address detector detects a destination address from a frame to be relayed. Here, when the destination is a terminal connected to the input / output port of the LAN connection device, there is no need to relay the frame to the main line. Therefore, when the detected destination address matches any of the transmission source addresses detected at the input / output ports, the control unit does not allow the trunk input / output port to relay.

Since the frames that need not be relayed to the main line are not relayed, the traffic on the main line is reduced. Therefore, the number of occurrences of collision at the time of frame relay is reduced.

In a configuration in which the source address detector is connected to each input / output port of the repeater, the source address is detected from a frame arriving for each input / output port.

In a configuration in which the source address detector is connected to the trunk of the repeater, the repeater detects the source address from the frame to be relayed to the trunk.

Further, a source address detector and a destination address detector provided at each of the plurality of input / output ports detect the source address and the destination address of the arriving frame. The detected source address is registered in the address search unit in association with the input / output port. Since the source address is the address of the terminal that transmitted the frame to the input / output port, the terminal connected to the input / output port of the LAN connection device is recognized. Further, the address search unit searches for an input / output port in which a source address that matches the detected destination address is registered. That is, the destination of the arrived frame is L
It is determined whether the terminal is connected to the input / output port of the AN connection device, and the input / output port is specified.

A plurality of second trunk lines are connected to the first trunk lines drawn from the respective input / output ports via the respective relay switches. The first trunk line and the second trunk line form a matrix circuit, and if one of the trunk switches at the intersection is closed, the first trunk line and one trunk line are connected via the trunk switch. One second trunk line is short-circuited. The control unit closes one relay switch, short-circuits the first relay line of the input / output port where the frame has arrived and the second relay line arbitrarily selected, closes another relay switch, and performs the search. The first trunk line of the input / output port and the second trunk line selected earlier are short-circuited. As a result, the input / output port at which the frame arrives and the searched input / output port are short-circuited. That is, the terminal transmitting the frame and the destination terminal are connected via the LAN connection device, and the relay of the frame is achieved.

During the relaying of this frame, if another frame arrives at a vacant I / O port and this another frame needs to be relayed to another vacant I / O port, The unit can close the relay switch in the unused second relay line, and connect the terminal transmitting the another frame to the terminal that is the destination. That is, collision between the frame being relayed and another frame is avoided. Therefore, the number of occurrences of collision at the time of frame relay is reduced.

When the control unit closes the relay switches of all the input / output ports when the address search unit cannot search for the corresponding input / output port, all the input / output ports are short-circuited.
The arriving frame will be relayed to all input / output ports. As a result, relaying to all I / O ports is performed only when the I / O port to be relayed cannot be specified, such as when there is no registered source address that matches the detected destination address. Relaying will be achieved if any terminal has a destination address at the output port.

When the arriving frame is a broadcast frame, that is, a frame addressed to all terminals, the control unit treats this frame as equivalent to the frame that could not be searched. That is, all the input / output ports are short-circuited by closing the relay switches of all the input / output ports. Therefore, this broadcast frame is relayed to all input / output ports.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

As shown in FIG. 1, each input / output port (port 1 to port N) of the LAN connection device 101 of the present invention
Are connected to respective ports of a repeater unit (repeater) 102 via corresponding bidirectional links 110. The repeater unit 102 relays a frame between ports in the same manner as the relay device 301 described above. One port of the repeater unit 102 is a bidirectional link 11
2 is connected.

For the purpose of detecting the station address of the terminal connected to the input / output port, the source station address detector (source address detector) 103
3 to the bidirectional link 110. In order to detect the destination station address of the frame relayed by the repeater unit 102, the bidirectional link 112 is used.
Is branched into a unidirectional link 114 and a unidirectional link 115 at a point A, and a destination station address detector (destination address detector) 105 is connected to the unidirectional link 114 among them.

In order to delay the relay frame while the repeater unit 102 determines whether or not to relay the relayed frame to the trunk line, the unidirectional link 1 is used.
The FIFO 104 is connected to 14. The a contact of the circuit 2 of the interlocking switch 107 is connected to the FIFO 104 via a unidirectional link 119 for the purpose of transmitting the relay frame delayed by the FIFO 104 to the trunk line. The common contact of the circuit 2 of the interlock switch 107 is connected to the point B of the bidirectional link 111 via the unidirectional link 117. The trunk port of the LAN connection device 101 is connected to this point B via a bidirectional link 111. A common contact of the circuit 1 of the interlocking switch 107 is connected to a point B via a unidirectional link 116 for the purpose of transmitting a frame from the trunk line to the repeater unit 102. The a contact of the circuit 1 of the interlock switch 107 is connected to the point A via the unidirectional link 115.

The bidirectional link 111 is the bidirectional link 406 in FIG. 6 or the bidirectional link 5 in FIG.
06 or the like.

In order to transmit a jam signal to the main line when a frame arrives from the main line while it is determined that the frame is not to be relayed to the main line, the b contact of the circuit 1 of the interlocking switch 107 is simply connected. The jam signal generator 108 is connected via a directional link 118, and the output of the jam signal generator 108 is connected via a unidirectional link 120 to the b-contact of the circuit 2 of the interlock switch 107.

For the purpose of determining whether or not to relay the frame to the trunk line, a control unit 106 is provided. To this control unit 106, a destination station address detector 105 is connected via a signal line 122. The source station address detector 103 of each input / output port is connected via a signal line 123. For the purpose of controlling the interlock switch 107,
The interlock switch 107 is connected to the control unit 10 via the signal line 121.
6 is connected. By the output of the control unit 106, the circuit 1 and the circuit 2 of the interlocking switch 107 are switched in conjunction with either the a contact or the b contact.

Next, the operation of the embodiment will be described.

In the LAN connection device 101, a frame arriving at any of the input / output ports (ports 1 to N) is transmitted to the repeater unit 1 by the bidirectional link 110.
02. At the same time, the unidirectional link 113
Thus, the frame is also transmitted to the source station address detector 103. The source station address detector 103 detects the source station address from this frame, holds it, and outputs it to the control unit 106 via the signal line 123. As a result, the station address of the terminal connected to the input / output port is registered.

On the other hand, the repeater unit 102 relays the arriving frame to the bidirectional link 110 and the bidirectional link 112 corresponding to the input / output port other than the input / output port at which the frame has arrived in the same manner as the relay device 301 described above.

The frame relayed to the bidirectional link 112 is transmitted to the FIFO 104 and the destination station address detector 105 via the unidirectional link 114 branched at the point A. The destination station address detector 105 detects the destination station address from this frame, and
To the control unit 106.

The control unit 106 controls the destination station address detector 1
05 and the output of each source station address detector 103, and if there is a match, that is, the frame relayed to the bidirectional link 112 is connected to the input / output port of the LAN connection device 101. If the frame is addressed to a terminal registered to be registered, the signal line 12
1 controls the interlock switch 107 to switch both the circuit 1 and the circuit 2 to the b contact. Conversely, when there is no match, that is, when the frame relayed to the bidirectional link 112 is addressed to a terminal other than the terminal registered to be connected to the input / output port of the LAN connection apparatus 101. In the case of, the circuit 1 and the circuit 2 are both held at the a contact without controlling the interlock switch 107.

When both the circuit 1 and the circuit 2 of the interlocking switch 107 are switched to the b-contact, the relay frame delayed by the FIFO 104 has no destination and is discarded. Therefore, the frame is not relayed to the trunk line.
Conversely, when the circuit 1 and the circuit 2 are both held at the contact a, the relay frame delayed by the FIFO 104 is transmitted to the trunk port via the unidirectional links 119 and 117 and the bidirectional link 111. Thus, the frame is relayed to the trunk line.

When both the circuit 1 and the circuit 2 of the interlocking switch 107 are switched to the contact b, that is, when it is determined that the frame is not to be relayed to the trunk side, and when the frame arrives at the trunk port, the arrival frame Is a jam signal generator 108 via a unidirectional link 116, a contact b of the circuit 1 of the interlocking switch 107, and a unidirectional link 118.
Is transmitted to The jam signal generator 108 generates a jam signal, and the jam signal is transmitted to the unidirectional link 120, the contact b of the circuit 2 of the interlocking switch 107, and the unidirectional link 117.
Is transmitted to the trunk port via The trunk side is notified that the relay to the repeater unit 102 was unsuccessful.

As the repeater unit 102, a commercially available repeater LSI can be used. Commercially available repeater LSIs include Am79C98 manufactured by AMD.
And DP83950 manufactured by National Semiconductor.

In the above embodiment, when a frame arrives and the detected destination address matches one of the registered transmission source addresses, the frame is not relayed to the input / output port of the trunk line. For this reason, the traffic on the trunk line is reduced, and the number of collision occurrences at the time of frame relay is reduced.

Next, another embodiment of the present invention will be described.

The LAN connection device 201 shown in FIG.
It has a plurality of input / output ports and a repeater unit 202,
One input / output port is connected to the trunk line. Figure 1 above
2, the source station address detector 103 is connected to each input / output port of the repeater unit 102, whereas in the example of FIG. 2, the source station address detector 203 is connected to the trunk side of the repeater unit 202. Connected. A source station address detector 203 corresponding to each input / output port is integrated in a source station address detector 209, and the source station address detector 209 is connected to the repeater unit 202 via a unidirectional link 224 and a bidirectional link 202. Is connected to one of the ports. Also, the repeater unit 202
The repeater unit 202 and the source station address detection unit 209 are connected via the signal line 213 for the purpose of notifying the source station address detection unit 209 of which port has arrived. The configuration on the main line side from point A is the same as the example in FIG.

In FIG. 2, a frame arriving at one of the input / output ports is transmitted to the repeater unit 202 via the bidirectional link 210. Repeater unit 20
2, a bidirectional link 210 and a bidirectional link 2 corresponding to input / output ports other than the input / output port at which the frame has arrived.
It relays to 12. The frame relayed to the bidirectional link 212 is transmitted to the source station address detection unit 209 via the unidirectional link 214. At the same time, the repeater unit 202 notifies the source station address detection unit 209 of which port the frame has arrived. Based on this information, the source station address detector 209 determines the source station address detector 20 corresponding to the input / output port where the frame has arrived.
3 is selected and the source station address is detected and registered from the frame transmitted from the unidirectional link 214.

The control unit 206 includes a destination station address detector 2
The output of the source station address detector 203 integrated with the output of the source station address detector 203 is compared, and if there is a match, the frame is not relayed to the trunk line.

According to the configuration of FIG. 2, since each source station address detector 203 is located at one location, only one waveform shaping circuit and one timing synchronizing circuit for reading information from a frame are required. Become.

Next, another embodiment of the present invention will be described.

The LAN connection device 1101 shown in FIG.
Is connected to a plurality of input / output ports (ports 1 to n) corresponding to the plurality of bidirectional links 1108, respectively.
102 is provided, and the bidirectional link 1108 is
One-way link 1125 and one-way link 11 within 102
It branches to 27. The unidirectional link 1125 is connected to a source station address detector 1111 for detecting a source station address of an arrival frame, a destination station address detector 1112 for detecting a destination station address, and a FIFO 1113 for delaying a frame. ing. FIFO11
The output side of 13 is connected to a unidirectional link 1126, and the unidirectional link 126 is merged with the unidirectional link 1127 and connected to a bidirectional link (first trunk line) 1104. Note that the unidirectional link 1127 is used for output from the input / output port.

The output of each source station address detector 1111 is connected to a station address search circuit (address search unit) 1106 for registering the source station address in correspondence with the input / output port.

The bidirectional link 1104, which is the first relay line of each input / output port, is provided with four relay switches 1103a to 1103d, respectively.
All the relay switches 1103a on 104 are connected to the bidirectional link 1105a (second relay line # 1). Similarly, the relay switch 1103b and thereafter are also connected to the bidirectional link 105b and later (second relay line # 2 and later). First trunk line 1104 and second trunk line 11
05a to 1105d form a matrix circuit, and if any of the relay switches at the intersection is closed, one first relay line and one second relay line are connected via the relay switch. Are short-circuited.

In order to control the relay switches 1103a to 1103d, a control unit 1107 is provided so as to be connected to a signal line 1123.
2, the destination station address detector 1112, the signal line 11
24, the station address search circuit 1106 is connected.

Next, the operation when a terminal connected to port 1 transmits a frame to a terminal connected to port 2 will be described. The frame arriving at port 1 is sent to a source station address detector 1111 and a destination station address detector 1111.
12 and each of the FIFOs 1113. The source station address detector 1111 detects the source station address and notifies the station address search circuit 1106. The terminal connected to the port 1 is registered in the station address search circuit 1106. The destination station address detector 1112 detects the destination station address and notifies the control unit 1107.

The control unit 1107 first passes the destination station address to the station address search circuit 1106 and requests the station address search. The station address search circuit 1106 searches the registered station addresses for one that matches the destination station address, and if there is a corresponding one, returns the input / output port to the control unit 1107. In this example, since the destination station address is a terminal connected to port 2, port 2
If the above has been registered, port 2 is answered. Therefore, the control unit 1107 controls the second trunk line # 1
To # 4, an unused one (here, # 1) is selected, and the relay switch 1103a on the second trunk line # 1 corresponds to the input / output port where the frame has arrived and the searched input / output port. The relay switch 1103a is closed. In this example, the relay switch 1103a corresponding to the port 1 and the port 2 is closed, and each terminal is connected to the LAN.
A short circuit has occurred through the connecting device.

During the period when the above-mentioned relay route is formed, F
In the IFO 1113, the arrival frame is delayed. After the delay, the frame output to the unidirectional link 1126 is relayed to the transmission / reception unit 1102 of the port 2 via the bidirectional link 1104-relay switch 1103a-bidirectional link 1105a-relay switch 1103a-bidirectional link 1104. You. The transmission / reception unit 1102 of the port 2 outputs the frame via a unidirectional link 1127 (not shown).

In the above operation example, while frame relay is being performed using the relay line # 1, the relay can be performed using the other relay lines # 2 to # 4. For example, when the terminal connected to the port i transmits a frame to the terminal connected to the port n, the bidirectional link 1104 corresponding to the port i, the relay switch 1103b corresponding to the port i, the bidirectional link 1105b and the port n from the transmission / reception unit 1102 corresponding to port i via the bidirectional link 1104 corresponding to the relay switch 1103b corresponding to port n
The relay to is performed.

Next, the detailed operation of the control unit 1107 will be described with reference to FIG.
This will be described with reference to FIG.

After the station address is notified from the destination station address detector 1112, the station address is searched by the station address search circuit 1106 in judgment 2201. If the search is successful, the process proceeds to decision 2202. If the search is not successful, the process proceeds to decision 2203 for the purpose of relaying to all ports.

At decision 2202, trunk lines # 1-#
One is secured from 4 and the process proceeds to decision 2204. If it cannot be secured, the process proceeds to processing 2208 for the purpose of notifying that the relay has been unsuccessful. on the other hand,
Similarly, in the judgment 2203, any one of the trunk lines # 1 to # 4 is secured, and the process proceeds to the decision 2205. If not, the process proceeds to the process 2208.

If it is determined in the decision 2204 that the port of the relay destination is not used, it is determined that the relay is possible and the processing 2
Proceed to 206. When the relay destination port is being used, it is determined that the relay is impossible, and the process proceeds to processing 2208. On the other hand, in the determination 2205, when all ports except the relay destination, that is, the transmission source are not used, it is determined that the relay is possible, and the process proceeds to a process 2207. If at least one of the ports excluding the transmission source is used, it is determined that relaying is impossible, and processing 2208 is performed.
Proceed to.

In the process 2206, as described above, the relay switch is selectively closed to form a relay route. On the other hand, in the process 2207, all the relay switches on the secured relay line are closed to form a relay route to all ports.

It should be noted that a frame in the Ethernet includes a frame (broadcast frame) to be transmitted to all stations on the same network. The destination station address of this frame is a specific station address. When a broadcast frame arrives, the frame has a station address that cannot be searched by the station address search circuit 1106. Therefore, the judgment 2201 in FIG.
You will proceed to 3.

The station address search circuit 1106 can be easily configured by using a memory called a content address memory (CAM). Further, the control unit 1107 can be configured using a microcomputer.

[0071]

The present invention exhibits the following excellent effects.

(1) Since frames that do not need to be relayed to the trunk line are not relayed, traffic on the trunk line is reduced, and the number of times of frame collisions is reduced.

(2) While a frame is being relayed between a pair of ports, a frame can be relayed between another pair of ports, so that the number of occurrences of frame collisions is reduced.

(3) Since the LAN connection device is composed of simple hardware and does not require a buffer using a memory, relaying can be performed with a small delay.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram of a LAN connection device showing another embodiment of the present invention.

FIG. 3 is a configuration diagram of a LAN connection device showing another embodiment of the present invention.

FIG. 4 is a flowchart of a control unit according to another embodiment of the present invention.

FIG. 5 is a configuration diagram of a network using a relay device.

FIG. 6 is a configuration diagram of a network using a plurality of relay devices.

FIG. 7 is a configuration diagram of a network using a plurality of relay devices.

[Explanation of symbols]

 102 Repeater (repeater unit) 103 Source (station) address detector 105 Destination (station) address detector 106 Control unit

Claims (6)

(57) [Claims] 1. A LAN connection device comprising a plurality of input / output ports and a repeater for relaying a frame between the input / output ports by the repeater, wherein at least one input / output port is connected to a main line, and A source address detector for detecting a source address from a frame arriving at a port is provided, and a destination address detector for detecting a destination address from a frame to be relayed is provided. This destination address is detected at each of the input / output ports. LA having a control unit for preventing relaying at an input / output port of a trunk when any of the transmission source addresses is matched.
N connection device. 2. The LAN connection according to claim 1, wherein said source address detector is connected to each input / output port side of the repeater, and detects a source address from a frame arriving for each input / output port. apparatus. 3. The LAN connection device according to claim 1, wherein the source address detector is connected to the trunk line of the repeater, and the repeater detects the source address from a frame to be relayed to the trunk line. 4. A source address detector and a destination address detector for detecting a source address and a destination address of an arrival frame at each of a plurality of input / output ports, and the source addresses correspond to the input / output ports. And an address search unit for searching for an input / output port in which a source address matching the destination address is registered, and a first trunk line is extracted from each input / output port, and the first trunk line is connected to the first trunk line. A plurality of second relay lines are bridged through the respective relay switches, and the first relay line of the input / output port where the frame has arrived and the first relay line of the searched input / output port are connected to the second relay line. A LAN connection device comprising a control unit for closing a relay switch to short-circuit a line. 5. The LAN connection device according to claim 4, wherein the control unit closes the relay switches of all the input / output ports when the address search unit cannot search for the corresponding input / output port. 6. The LA according to claim 4, wherein when the arrival frame is a broadcast frame, the control unit closes the relay switches of all the input / output ports.
N connection device.