JPH0575616A - Mac bridge - Google Patents

Abstract

PURPOSE:To prevent a network from forming a loop thereby even when a connection is made to form a loop structure in mistake due to mis-connection or mis-management. CONSTITUTION:In the MAC bridge in which plural LANs are connected by an ISDN line, a function to detect a loop structure of the network is provided to the bridge. That is, when ISDN line connection is finished in an ISDN line connection section 6, a topology confirmation frame transmission section 10 sends a topology confirmation frame to a LAN 2 to allow a timer section 9 to start counting. When the topology confirmation frame sent by itself is received before a timer of the timer section 9 expires, it is discriminated that the network is in loop and a frame relay of a frame relay processing section 5 is inhibited. When the topology confirmation frame sent by itself is not received even when the timer of the timer section 9 expires, the frame relay by the frame relay processing section 5 is started.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses a plurality of LANs for ISD.
Used for the MAC bridge connected by N line. The present invention relates to a MAC bridge capable of preventing a failure due to a connection error or a management error from occurring.

[0002]

2. Description of the Related Art Conventionally, in this type of MAC bridge, a plurality of connections are made through an ISDN line without performing any check, and a frame relay process is executed.

[0003]

DISCLOSURE OF THE INVENTION The conventional MAC described above
In the bridge, due to the nature of the ISDN line, the connection destination is ISD
Since it can be changed depending on the N number, when multiple MAC bridges are used, the network takes a loop structure due to a number error or a management error, so that the frame goes around the network and causes a protocol failure, or a network failure occurs. There was a problem that the whole became excessive traffic and went down.

The present invention solves such a problem, and an object of the present invention is to provide a bridge capable of preventing a failure due to a connection error or a management error from occurring.

[0005]

According to the present invention, there is provided a LAN connecting section for connecting to a local area network (LAN), an ISDN line connecting section for connecting to an ISDN line, and a frame relay including a filtering process. In a MAC bridge having a frame relay processing unit for performing,
A topology confirmation frame transmission unit that receives a line connection completion signal from the ISDN line connection unit at the time of startup and sends a topology confirmation frame to all the LANs that are connected once or multiple times, and relays the topology confirmation frame and sends it out by itself. Topology confirmation frame processing unit that detects the topology confirmation frame, a timer unit that starts counting when a count start signal is received and sends a timer expiration signal after a lapse of a predetermined time, and temporarily prohibits frame relay at startup. , When it receives the topology confirmation frame sent by itself, it judges that the network forms a loop and prohibits relaying of the frame, and does not receive the topology confirmation frame sent by itself until the time of the timer section expires. The network is not in a loop. Characterized in that a frame relay instruction section to start relaying over arm.

The topology confirmation frame transmission unit includes means for outputting a topology confirmation frame transmission signal to the frame relay instruction unit when receiving a line connection completion signal from the ISDN line connection unit, and the frame relay instruction unit. Outputs a count start signal to the timer unit when it receives a topology confirmation frame transmission signal from the topology confirmation frame transmission unit, and receives a loop detection signal from the topology confirmation frame processing unit from the timer unit. It is desirable to include means for outputting a frame relay start signal to the frame relay processing unit and the topology confirmation frame processing unit when a timer expiration signal is received.

[0007]

When the ISDN line connection is completed, the topology confirmation frame is sent to all the connected LANs.
When a topology confirmation frame sent by the own blitch is received from a port other than the sending port, it is judged that the network has a loop structure and the frame relay process is prohibited. When the topology confirmation frame sent by the self-blit is not received after a certain period of time, it is determined that the network does not form a loop and the frame relay process is started.

This makes it possible to prevent the network from forming a loop even if a connection is mistakenly made to form a loop structure due to a mistake in number, a mistake in management or the like, and a failure occurs. Can be prevented in advance.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment of the present invention.

In the embodiment of the present invention, the LAN connecting section 4 for connecting to the LAN 2 and the IS for connecting to the ISDN line 3 are connected.
A DN line connection unit 6 and a frame relay processing unit 5 that relays a frame including a filtering process are provided. Further, as a feature of the present invention, a topology confirmation frame that receives a line connection completion signal from the ISDN line connection unit 6 at startup Confirming frame sending unit 10 for sending out to all the LANs 2 connected once or a plurality of times, and a topology confirming frame processing unit 7 for relaying the topology confirming frame and detecting the topology confirming frame sent by itself.
And a timer unit 9 that starts counting when receiving a count start signal and sends a timer expiration signal after a predetermined time has elapsed.
Then, when relaying frames is temporarily prohibited at startup, when the topology confirmation frame sent by itself is received, it is determined that the network forms a loop, and frame relay is prohibited, until the time of the timer unit 9 expires. And a frame relay instructing unit 8 that starts relaying the frame when it judges that the network is not in a loop when it does not receive the topology confirmation frame sent by itself to the ISDN line. The frame relay instructing unit 8 includes means for outputting a topology confirmation frame transmission signal to the frame relay instructing unit 8 when receiving the line connection completion signal from the connecting unit 6, and the frame relay instructing unit 8 includes the topology confirmation frame transmitting unit 10 to output the topology confirmation frame. When it receives the send signal, it outputs a count start signal to the timer unit 9 and outputs the topology confirmation flag. In a state where the over arm section 7 is not subject to loop detection signal comprises means for outputting a frame relay start signal to the frame relay processing unit 5 and topology confirmation frame processing section 7 upon receiving a timer expiration signal from the timer unit 9.

Next, the operation of the embodiment of the present invention thus constructed will be described.

The LAN connection section 4 is an interface section to the LAN 2 and transmits / receives a frame to / from the LAN 2. The ISDN line connection unit 6 is an interface unit to the ISDN line 3, sends and receives the ISDN line 3, and transmits / receives a frame. When the ISDN line 3 establishes a link with a MAC bridge that opposes the topology confirmation frame transmission unit 10. Output a line connection completion signal to.

The frame relay processing section 5 includes a LAN connection section 4
And the ISDN line connection unit 6 have a function of performing a frame relay process including a filtering process, and temporarily inhibit the frame relay according to the frame relay temporary inhibit signal from the frame relay instruction unit 8, The relay of the frame is started according to the frame relay start signal from 8, and the relay of the frame is prohibited according to the frame relay prohibition signal from the frame relay instruction unit 8.

The topology confirmation frame processing unit 7 operates while the frame relay instruction unit 8 outputs the frame relay temporary prohibition signal, and the LAN connection unit 4 and the ISDN line connection unit 6 exchange the topology confirmation frame with each other. When it receives a topology confirmation frame output by itself, it outputs a loop detection signal to the frame relay instructing unit 8.

The frame relay instruction unit 8 sends a frame relay temporary prohibition signal to the frame relay processing unit 5 and the topology confirmation frame processing unit 7 after the initialization of the MAC bridge 1, and the topology confirmation frame transmission unit 10 transmits the topology confirmation frame. When a signal is received, a count start signal is output to the timer unit 9, and when a loop detection signal is received from the topology confirmation frame processing unit 7, a frame relay prohibition signal is output to the frame relay processing unit 5 and the topology confirmation frame processing unit 7, and the topology is confirmed. When the timer expiration signal is received from the timer unit 9 without receiving the loop detection signal from the confirmation frame processing unit 7, the frame relay start signal is output to the frame relay processing unit 5 and the topology confirmation frame processing unit 7.

The timer unit 9 starts counting when it receives a count start signal from the frame relay instruction unit 8, and when the timer expires after a certain period of time, the frame relay instruction unit 8
The timer expiration signal is output to.

The topology confirmation frame transmission section 10 is
When the line connection completion signal is received from the DN line connection unit 6,
All or two times a topology confirmation frame in which all MAC bridges relay as destination addresses and have own MAC bridge addresses as source addresses LAN2
In addition to the above transmission, a topology confirmation frame transmission signal is output to the frame relay instruction unit 8.

FIG. 4 is a block diagram showing the structure of a conventional example. The MAC bridge 11 that relays the LAN 12 and the ISDN line 13 includes a LAN connection unit 14 and a frame relay processing unit 1.
5 and the ISDN line connection unit 16.

The LAN connection section 14 is an interface section of the LAN 12 and transmits / receives frames to / from the LAN 12. The frame relay processing unit 15 performs frame relay control including filtering processing between the LAN connection unit 14 and the ISDN line connection unit 16. ISDN line connection 1
Reference numeral 6 denotes an interface portion to the ISDN line 13, which sends and receives the ISDN line 13 and transmits and receives frames.

FIG. 2 is a diagram showing a configuration example of a network having a loop structure. In this example, MAC bridges 19, 20, 21, 22 and I connecting LANs 17 and 18 are connected.
It is composed of SDN lines 23 and 24.

FIG. 3 is a diagram showing a configuration example of a normal network having no loop structure. In this example, LANs 25 and 2 are used.
MAC bridges 28, 29, 30, connecting 6, 27,
31 and ISDN lines 32 and 33.

The MAC bridge of the conventional example is erroneously shown in FIG.
In the case of constructing the configuration as shown in (1), there is no function of detecting the generation of the loop structure when the MAC bridges 21 and 22 are started up later after the MAC bridges 19 and 20 are operating. Therefore, the network is connected as it is, the network has a loop structure, the frames on the LANs 17 and 18 circulate, and a communication failure occurs.

According to the present invention, a MAC bridge is erroneously constructed as shown in FIG.
MAC bridge 2 later with 20 and 20 running
The operation when 1 and 22 are started up will be described.

First, the MAC bridge 21 starts up and the ISDN line 24 is connected. Inside the MAC bridge 21, a line connection completion signal is sent from the ISDN line connection unit 6 to the topology confirmation frame sending unit 10.
The topology confirmation frame transmission unit 10 transmits the topology confirmation frame to the LAN 17 via the LAN connection unit 4 and also outputs the topology confirmation frame transmission signal to the frame relay instruction unit 8.

The topology confirmation frame output on the LAN 17 is the MAC bridge 19 which is already in the operating state,
As a normal frame having no special meaning for 20, the MAC bridge 19, the ISDN line 23, and the MAC bridge 20 are relayed in this order and transmitted to the LAN 18.

The topology confirmation frame output on the LAN 18 is taken into the MAC bridge 22 and the MAC
ISDN via the LAN connection unit 4, the topology confirmation frame processing unit 7, and the ISDN line connection unit 6 in the bridge 22.
It is sent out on the line 24. The topology confirmation frame transmitted on the ISDN line 24 is again transmitted to the MAC bridge 21.
It is taken in and transferred from the ISDN line connection unit 6 to the topology confirmation frame processing unit 7 inside the MAC bridge 21.

The topology confirmation frame processing unit 7 relays the topology confirmation frame to the LAN connection unit 4 and also detects that the topology confirmation frame is output by itself.
The loop detection signal is output to the frame relay instruction unit 8. Upon receiving the loop detection signal, the frame relay instruction unit 8 outputs a frame relay prohibition signal to the frame relay processing unit 5 and the topology confirmation frame processing unit 7. Upon receiving the frame relay prohibition signal, the frame relay processing unit 5 prohibits frame relay. At the same time, the topology confirmation frame processing unit 7 which receives the frame relay prohibition signal prohibits the operation. MA
The same operation is prohibited on the C bridge 22 side as well.

As described above, even if the configuration shown in FIG. 2 is mistakenly taken, it is possible to prevent the network from becoming a loop and prevent a failure from occurring.

Next, the MAC bridge of the embodiment of the present invention is used to construct as shown in FIG.
The operation when the MAC bridges 30 and 31 are started up later while 8 and 29 are operating will be described.

First, the MAC bridge 30 starts up and the ISDN line 33 is connected. Inside the MAC bridge 30, a line connection completion signal is sent from the ISDN line connection unit 6 to the topology confirmation frame sending unit 10.
The topology confirmation frame transmission unit 10 transmits the topology confirmation frame to the LAN 26 via the LAN connection unit 4 and outputs the topology confirmation frame transmission signal to the frame relay instruction unit 8.

Upon receiving the topology confirmation frame transmission signal, the frame relay instruction unit 8 outputs a count start signal to the timer unit 9. The timer unit 9 that has received the count start signal starts counting. Since there is no relay destination from the LAN 26, the topology confirmation frame disappears here. On the other hand, M
The same operation is performed in the AC bridge 31. The topology confirmation frame transmitted from the MAC bridge 31 to the LAN 27 is the MAC bridge 2 already in operation.
As a normal frame having no special meaning for 8 and 29, the MAC bridge 29, the ISDN line 32, and the MAC bridge 28 are relayed in this order and transmitted to the LAN 25. Since there is no relay destination from the LAN 25, the topology confirmation frame disappears here.

The MAC bridge 30 continues in this state.
When the timer of the timer unit 9 therein expires, a timer expiration signal is output to the frame relay instruction unit 8. The frame relay instructing unit 8 that has received the timer expiration signal causes the frame relay processing unit 5 to
And a frame relay start signal is output to the topology confirmation frame processing unit 7. Upon receiving the frame relay start signal, the topology confirmation frame processing unit 7 stops its operation. Further, the frame relay processing unit 5 that has received the frame relay start signal
Start the frame relay operation. Similarly, MAC bridge 3
Even within 1, the frame relay operation of the MAC bridge 31 is started by the expiration of the timer. This allows LAN2
A network in which 5, 26 and 27 are connected is realized.

[0033]

As described above, according to the present invention, it is possible to prevent a network from forming a loop even if a connection is mistakenly formed to form a loop structure due to a mistake in number or a mistake in management. Therefore, there is an effect that it is possible to prevent the occurrence of a failure.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration example of a network having a loop structure.

FIG. 3 is a diagram showing a configuration example of a network having no loop structure.

FIG. 4 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

1, 11, 19, 20, 21, 22, 28, 29, 3
0, 31 MAC bridge 2, 12, 17, 18, 25, 26, 27 LAN 3, 13, 23, 24, 32, 33 ISDN line 4, 14 LAN connection unit 5, 15 Frame relay processing unit 6, 16 ISDN line Connection unit 7 Topology confirmation frame processing unit 8 Frame relay instruction unit 9 Timer unit 10 Topology confirmation frame transmission unit

Claims (3)

[Claims] 1. A local area network (LAN)
In a MAC bridge having a LAN connection unit for connection with an ISDN line, an ISDN line connection unit for connection with an ISDN line, and a frame relay processing unit for relaying a frame including a filtering process, the ISDN line connection is made at startup. Topology confirmation frame sending unit that receives a line connection completion signal from the unit and sends the topology confirmation frame to all the LANs connected once or multiple times, and relays the topology confirmation frame and detects the topology confirmation frame sent by itself. Topology confirmation frame processing unit that performs the above, a timer unit that starts counting when a count start signal is received and sends a timer expiration signal after a lapse of a predetermined time, and temporarily disables frame relay at startup and confirms the topology sent by itself. When a frame is received, the network will form a loop Frame relay is prohibited, and if the topology confirmation frame sent by itself is not received before the time of the timer expires, it is judged that the network is not in a loop and frame relay is started. A MAC bridge comprising a frame relay instruction unit for 2. The topology confirmation frame transmission section includes means for outputting a topology confirmation frame transmission signal to the frame relay instruction section when receiving a line connection completion signal from the ISDN line connection section. MAC bridge. 3. The frame relay instructing unit outputs a count start signal to the timer unit when receiving a topology confirmation frame transmission signal from the topology confirmation frame transmission unit, and causes the topology confirmation frame processing unit to detect a loop. 2. The MAC bridge according to claim 1, further comprising means for outputting a frame relay start signal to the frame relay processing unit and the topology confirmation frame processing unit when a timer expiration signal is received from the timer unit without receiving a signal.