JP2005033360A - Bridge apparatus and method for processing bridge thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that in a network extended by using a bridge, there might recently be an environment which cannot use the spanning tree protocol of a standard protocol for detecting and cutting a loop, in which environment when the loop is generated in the network due to a construction fault, etc., a function of the network is always downed. <P>SOLUTION: In the network having the loop, a port transition of an address learning entry frequently occurs in an address learning table in the bridge. The bridge apparatus contrarily detects the loop by monitoring the occurring frequency of the port transition of the address learning entry in the address learning table at each port, transits the detected port to a blocking state (a state that a frame is not relayed), and logically disconnects the loop, thereby avoiding downing of the network. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bridge device for connecting a plurality of networks at a layer 2 level and a bridge processing method for the device, and in particular, a technique for detecting a loop on the network and logically disconnecting such a loop. About.
[0002]
[Prior art]
The bridge device is a device that connects a plurality of networks at a layer 2 level. In a network expanded using a bridge device, if a loop occurs on the network due to a construction error or the like, frames continue to travel on the network endlessly and normal communication cannot be performed. As a conventional technique for solving this problem, there is a spanning tree protocol (see, for example, Non-Patent Document 1).
[0003]
The Spanning Tree Protocol is based on the assumption that bridge devices exchange BPDU (Bridge Protocol Data Unit) frames periodically, monitor loops on the network, and if a loop is detected, cause the loop. By shifting the ports that are in a blocking state (a state in which no frame is relayed), a logically loop-free state is maintained.
[0004]
[Non-Patent Document 1]
IEEE (American Institute of Electronics and Electrical Engineers) 802.1D
[0005]
[Problems to be solved by the invention]
In recent years, communication service providers have provided services for transparently connecting a plurality of geographically dispersed networks at the layer 2 level. In particular, a service for transferring an Ethernet frame is referred to as a wide area Ethernet service.
[0006]
As a platform for providing such a communication service, a communication service provider uses a self-operated wide area network. In that case, the spanning tree protocol cannot be used in the process.
[0007]
This is because when the spanning tree protocol is used, the BPDU frame of the spanning tree protocol included in the customer traffic is processed by the bridge device in the communication service provider, and all frames are transmitted at the layer 2 level. This is because the original service cannot be provided.
[0008]
Therefore, the spanning tree protocol function is stopped for each bridge device in the communication service provider, and the BPDU included in the customer traffic is relayed in the same manner as a normal data frame. Required.
As described above, the spanning tree protocol cannot always be used in a network environment in recent years. In that case, it is a problem that the system is extremely weak against a loop generated on the network due to a construction error or the like.
[0009]
The present invention has been made to solve this problem. That is, an object of the present invention is to detect a loop on the network without using the spanning tree protocol, and to cause a loop generated on the network by transitioning a port to a blocking state when the loop is detected. The present invention provides a bridge device having a function of logically disconnecting and processing method thereof.
[0010]
[Means for Solving the Problems]
In a network having a loop that circulates indefinitely, in a conventional bridge device, port transitions of address learning entries frequently occur in an address learning table in the bridge device.
[0011]
In the present invention, on the contrary, in the bridge device, the frequency of occurrence of the port transition of the address learning entry in the address learning table is monitored for each port to detect a loop and block the detected port (block is not relayed). State) and logically cut a loop generated on the network to avoid network down. In this way, loop detection and logical disconnection is performed at the bridge without using the spanning tree protocol.
[0012]
Specifically, the bridge device having the loop detection and disconnection function according to the present invention records the first step for detecting the occurrence of port transition of the address learning entry in the address learning table and the number of occurrences for each port. The counter value for each of the counter table and the port before the transition when the port transition of the address learning entry is detected in the first step and the port after the transition are incremented by one. A third step of constantly monitoring the counter table and recognizing that there is a loop on the network when a predetermined threshold value is reached, and transitioning the port to a blocking state; and A fourth step for periodically resetting the counter value; and the third step. When a port is transitioned to the blocking state by a group, the contents are reported to the administrator using a console message, a SYSLOG packet, and an SNMP trap packet, and the port that has transitioned to the blocking state is operated by the administrator's operation. When it is confirmed that the increase amount within a certain period of the counter value in the counter table does not reach the preset upper limit value for the command for returning and the port changed to the blocking state, And a sixth step of automatically releasing and restoring the port blocking state.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0014]
1 and 2 are network configuration diagrams for explaining the operation of a bridge having a loop detection and disconnection function according to the present invention. The bridge 20 in the figure corresponds to the bridge of the present invention. FIG. 1 shows a normal network configuration without a loop, and FIG. 2 shows a state where a construction error has occurred in the network configuration of FIG. 1 and the network has shifted to an abnormal network with a loop.
[0015]
First, the network configuration of FIG. 1 will be described. There are four networks to which two personal computers are connected, and each network (11a, 11b, 11c, 11d) is connected to the bridge device 20. In this example, VLAN (Virtual Local Area Network) technology is used, and the bridge device 20 connects the network 11a and the network 11b at the layer 2 level, and the network 11c and the network 11d are also connected at the layer 2 level.
[0016]
That is, there is a VLAN 13a in which the network 11a and the network 11b are grouped at the layer 2 level, and a VLAN 13b in which the network 11c and the network 11d are grouped at the layer 2 level, and communication at the layer 2 level between the VLAN 13a and the VLAN 13b is performed. Blocked. That is, mutual communication between the personal computer 10a, the personal computer 10b, the personal computer 10c, and the personal computer 10d is possible, and similarly, mutual communication between the personal computer 10e, the personal computer 10f, the personal computer 10g, and the personal computer 10h is possible.
[0017]
FIG. 2 shows a state in which a link (short-circuit path) 14 appears due to a construction mistake and a loop occurs in the network in the network configuration of FIG. In this case, if the bridge device 20 continues to relay the frame between the port 12a and the port 12b, the frame continues to loop (infinitely circulate) on the network, and the normal communication within the VLAN 13a cannot be performed. In the bridge device 20, the port transition of the address learning entry occurs frequently, resulting in an overload state, leading to a decrease in frame relay performance, and adversely affecting the communication of the VLAN 13b unrelated to the VLAN 13a in which the loop is generated.
[0018]
FIG. 3 is a functional block diagram of the bridge device 20 having a loop detection and disconnection function according to the present invention. For comparison, a functional block diagram of a conventional bridge device 200 is shown in FIG. As can be seen by comparing FIG. 3 and FIG. 4, the function blocks newly added for the present invention are the address learning table monitoring unit 31, the counter table 32, the loop detection / disconnection unit 33, the counter reset unit 34, and automatic recovery. They are a control unit 35 and a changeover switch 36.
[0019]
The ports 12a to 12d are connection points between the bridge device and the network, and are interfaces for transmitting and receiving frames. The address learning processing unit 21 operates when a frame is received from each port (12a, 12b, 12c, 12d), and records information on the transmission source address and the reception port of the received frame in the address learning table 22.
[0020]
For example, in FIG. 1, when the personal computer 10a transmits a frame, the bridge 20 receives the frame from the port 12a, and registers the address of the personal computer 10a and the information of the receiving port 12a in the address learning table 22.
[0021]
In this way, in FIG. 1, when all the personal computers transmit frames, the address learning table 22 of the bridge 20 is in a state as shown in FIG. In the case of a normal network without a loop as shown in FIG. 1, since the port through which the bridge 20 receives frames from each personal computer is fixed for each personal computer, the address learning table 22 is stable in the state of FIG.
[0022]
As shown in FIG. 5, the address learning table 22 is an area for storing which node is connected to which port, and is a set of address learning entries 25.
[0023]
When the forwarding processing unit 23 receives a frame from the ports 12a to 12d, the forwarding processing unit 23 checks whether the destination address of the frame is registered in the address learning table 22, determines a relay destination port, and determines the frame from the determined port. Send.
[0024]
At this time, useless frame relay processing is omitted. For example, a frame transmitted from the personal computer 10a to the personal computer 10b can be determined by referring to the address learning table 22 so that the destination node exists ahead of the port 12a that received the frame. Discard without relaying.
[0025]
The aging processing unit 24 is for deleting an address learning entry that has not been updated for a certain period of time in the address learning table 22, that is, an address learning entry that has become less reliable as time passes.
[0026]
If the old information is kept, the following communication failure may occur. For example, consider the case where the personal computer 10b is physically moved from the network 11a side to the network 11b side in FIG.
[0027]
FIG. 6 shows an image diagram at this time. At this time, if the bridge 20 continues to hold old erroneous information that the personal computer 10b stored in the address learning table 22 exists on the port 12a side, the frame transmitted by the personal computer 10a to the personal computer 10b is transmitted to the network 11b side. Communication is not established because it is not relayed to.
[0028]
In this case, when the personal computer 10b transmits the first frame after moving, the bridge 20 can rewrite the contents of the address learning table 22 with correct information, and the port transmitted by the personal computer 10a to the personal computer 10b is correctly ported. 12b is relayed to establish communication. In order to eliminate such a communication failure, it is necessary for the aging processing unit 24 to delete outdated information.
[0029]
Next, port transition of an address learning entry used as a means for detecting a loop by the bridge according to the present invention will be described. For example, a case where the personal computer 10a transmits a broadcast frame (a frame addressed to all nodes in the same VLAN) in a network configuration with a loop as shown in FIG. 2 will be described.
[0030]
Note that the bridge that has received the broadcast frame must relay to all other ports grouped in the VLAN.
[0031]
As shown in FIG. 2, the broadcast frame transmitted by the personal computer 10a passes through the path 15 and arrives at both the port 12a and the port 12b of the bridge 20. When the bridge 20 receives this frame from the port 12a, the bridge 20 records the address of the personal computer 10a and the port 12a as its port information in the address learning table 22, and relays the frame to the port 12b.
[0032]
Similarly, when this frame is received from the port 12b, the address of the personal computer 10a and the port 12b as its port information are recorded in the address learning table 22, and the frame is relayed to the port 12a. Since the network 11a and the network 11b are connected by the link 14, the frame transmitted from the port 12a arrives again at the port 12b, and similarly, the frame transmitted from the port 12b also arrives at the port 12a.
[0033]
Thereafter, with this repetition, the bridge 20 relays the same frame again and again, and the address learning table 22 frequently causes port transitions of address learning entries as shown in FIG.
[0034]
FIG. 7 shows how the port information of the address learning entry 25 having the address of the personal computer 10a is rewritten from the port 12a to the port 12b or from the port 12b to the port 12a. As described above, in a network having a loop, port transitions of address learning entries frequently occur. In the present invention, the occurrence of port transition in such an address learning entry is observed, and on the contrary, loop detection is performed and the loop generated on the network is logically disconnected, which will be described in detail below.
[0035]
The address learning table monitoring unit 31 is a newly added functional block for the present invention. The address learning table monitoring unit 31 monitors the occurrence state of port transition of the address learning entry in the address learning table 22 and records the number of occurrences in the counter table 32 for each port. As a specific operation, every time a port transition of the address learning entry is detected, the counter value in the counter table 32 is incremented by 1 for both the port before transition and the port after transition.
[0036]
This counter table 32 is also a newly added functional block for the present invention. The counter table 32 is a storage area for recording the number of occurrences of port transitions in the address learning entry for each port, and has a counter value for each port. FIG. 8 is a diagram showing an example for explaining the counter table 32. As can be seen from FIG. 8, the port 12c and the port 12d have a count value of “0”, whereas the port 12a and the port 12b have a counter value of “18” and “21” because a loop is generated by the link 14. Thus, it is in a state of being sequentially added.
[0037]
Next, the loop detection / cutting unit 33 is also a newly added functional block for the present invention. The loop detection / disconnection unit 33 constantly monitors the counter table 32, and when the counter value reaches a preset threshold value, determines that a loop has occurred and blocks the port (block is not relayed). By making the transition to, the loop generated on the network is logically disconnected. It also has a function of notifying the administrator that a loop has been detected by using a console message, a SYSLOG packet, and an SNMP trap packet. The administrator can restore a port that has transitioned to a blocking state using a command after removing a loop that has occurred in the network.
[0038]
Next, the counter reset unit 34 is also a newly added functional block for the present invention. The counter reset unit 34 periodically resets the counter value in the counter table 32 to zero. Thereby, the loop detection / disconnection unit 33 can recognize the occurrence state of the port transition of the address learning entry by the number of occurrences per unit time, that is, the occurrence frequency.
[0039]
Since the port transition of the address learning entry also occurs when the personal computer is moved instead of the loop as shown in FIG. 6, the occurrence frequency must be used to detect the occurrence of the loop more accurately.
[0040]
Next, the automatic return control unit 35 is also a newly added functional block for the present invention. The automatic return control unit 35 can be disabled or enabled by the changeover switch 36. By enabling the automatic return control unit 35 with the changeover switch 36, the port that has been shifted to the blocking state can be automatically returned.
[0041]
However, when performing the automatic return, the address learning process is continued even for the port that has been changed to the blocking state, and the counter reset unit 32 does not reset the counter value for the port that has been changed to the blocking state. It is necessary to set as follows.
[0042]
In this state, the automatic return control unit 35 stores the counter values measured before and after a certain period in a memory unit (not shown), and calculates the increase amount by calculating the difference between the stored counter values. . If the calculated increase is below the preset upper limit, it is determined that the loop has been removed, and the port is automatically released from the blocking state and returned to frame relay again. .
[0043]
Since the bridge 20 according to the present invention has the loop detection and disconnection functions as described above, even when the network configuration having a loop as shown in FIGS. Detection can be performed, and the ports 12a and 12b can be transitioned to the blocking state to maintain a logically loop-free network. At the same time, frequent port transitions of the address learning entry are prevented, and the bridge 20 does not become overloaded. Therefore, it is possible to avoid the performance degradation of the frame relay processing of the VLAN 13b in which no loop has occurred. Furthermore, when returning to a normal state without a loop as shown in FIGS. 2 to 1, the port blocking state can be automatically canceled and frame relay can be resumed.
[0044]
【The invention's effect】
According to the present invention, even in a bridge installed in a network environment where the spanning tree protocol cannot be used, a network loop due to a construction error or the like is detected without using the spanning tree protocol. Can be logically disconnected.
[0045]
This avoids frame loops and prevents the network from going down, and prevents the bridge from becoming overloaded due to frequent port transitions of address learning entries in the address learning table. Does not adversely affect frame relay processing of unrelated networks.
Further, according to the present invention, when a state with a loop returns to a state without a loop, this can be automatically detected and frame relay can be resumed.
[0046]
Furthermore, since the present invention detects a loop based on the frequency of occurrence of port transitions in the address learning entry, even if a port transition in the address learning entry that occurs temporarily by moving a node is detected, the loop is erroneously detected. There is no recognition. Furthermore, since the present invention uses the address learning function of a conventional bridge and detects a loop, it is easy to implement.
[Brief description of the drawings]
FIG. 1 is a network configuration diagram without a loop.
FIG. 2 is a network configuration diagram with a loop.
FIG. 3 is a functional block diagram of a bridge device having a loop detection and disconnection function according to the present invention.
FIG. 4 is a functional block diagram of a conventional bridge device.
FIG. 5 is an explanatory diagram for explaining an address learning table;
FIG. 6 is an exemplary diagram showing an example of movement of a personal computer.
FIG. 7 is an explanatory diagram for explaining port transition of an address learning entry in an address learning table.
FIG. 8 is an explanatory diagram for explaining a counter table.
[Explanation of symbols]
10 PC 11 Network 12 Port 13 VLAN
14 link 15 route 20 bridge 21 address learning processing unit 22 address learning table 23 forwarding processing unit 24 aging processing unit 25 address learning entry 31 address learning table monitoring unit 32 counter table 33 loop detection / disconnection unit 34 counter reset unit 35 automatic return control Part 36 selector switch

Claims (11)

A bridge device for connecting a plurality of networks to each other,
An address learning table that records a source address from a terminal device connected to the network and a received port number in association with each other;
An address learning table monitoring unit that monitors a transition state of the port number with respect to the transmission source address recorded in the address learning table, and counts the number of times of transition every time the port number transitions;
A bridge device comprising: a loop detection / disconnection unit that detects a loop caused by a short-circuit path on the network based on a count value counted by the address learning table monitoring unit. The loop detection / disconnection unit logically disconnects the loop by detecting the loop generated by the short circuit path on the network and then transitioning the port where the loop is generated to a blocking state in which no frame is relayed. The bridge device according to claim 1, which also has a function of: And a counter table for recording the count value for each port based on the count value counted by the address learning table monitoring unit, wherein the loop detection / disconnection unit is based on the count value recorded in the counter table. The loop generated by the short-circuit path on the network is detected, and the port in which the loop is generated is transited to a blocking state in which no frame is relayed to logically disconnect the loop. Item 3. The bridge device according to Item 2. The loop detection / cutting unit detects the loop caused by the short-circuit path on the network and the loop occurs when the count value recorded in the counter table reaches a preset threshold value. 4. The bridge device according to claim 3, wherein the loop is logically disconnected by transitioning a port to a blocking state in which no frame is relayed. 5. The bridge device according to claim 3, further comprising a counter reset unit that periodically resets the count value of the counter table. Furthermore, for the port that has been changed to the blocking state,
When it is confirmed that the increment amount of the counter value in the counter table within a certain period does not reach the preset upper limit value, it is determined that the loop has been removed, and the port blocking is automatically performed. The bridge device according to claim 3 or 4, wherein the state is released and returned. In a bridge processing method of a bridge device having an address learning table that records a correspondence between a source address and a received port number from a terminal device connected to each other by connecting a plurality of networks,
A monitoring step of monitoring the transition status of the port number with respect to the source address recorded in the address learning table, and counting the number of transitions for each port number;
And a detection step of detecting a loop caused by a short-circuit path on the network based on the counted value. Further, after detecting the loop caused by the short-circuit path on the network, a disconnection step of logically disconnecting the loop by transitioning the port where the loop occurs to a blocking state in which no frame is relayed, The bridge processing method according to claim 7, wherein: The detecting step includes a recording step of recording the count value counted in the counting step in a counter table, and the short circuit on the network when the count value recorded in the counter table reaches a preset threshold value. The bridge processing method according to claim 7, further comprising: a determination step of determining and detecting that the loop generated by the path is generated. The bridge processing method according to claim 9, further comprising a reset step of periodically resetting the count value recorded in the counter table in the recording step. Furthermore, the loop is removed when it is confirmed that the increment of the counter value in the counter table within a certain period of time does not reach the preset upper limit value for the port that has been changed to the blocking state. The bridge processing method according to claim 8, further comprising: an automatic return step that determines that the port is in a normal state and automatically cancels and restores the blocking state of the port.

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