JP2007235691A - Loop generating direction judgment system and loop separation system in mac bridge network - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a loop generating direction judgment system and a loop separation system in a MAC bridge network, in which direction in the network a loop is generated can be simply, quickly and economically detected. <P>SOLUTION: A test frame (a) is transmitted from a testing apparatus 6 to the MAC bridge network, and when the test frame (a) is returned to the testing apparatus 6, a loop generating direction judgment apparatus is started. When a transmission source MAC address of the test frame (a) in each of learning tables T1 to T4 of respective MAC bridging apparatuses is learned by a port which is not a port direction nearest to the testing apparatus 6 logically from a MAC bridging apparatus, the loop generating direction judgment apparatus judges the loop exists in the direction. Even when the MAC bridging apparatus itself composes a part of the loop, the loop can be detected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the MAC bridging network (Ethernet (registered trademark)), the present invention relates to a loop generation direction determination method for determining in which port direction of a MAC bridging device a loop is generated and a loop at an early stage. The present invention relates to a loop disconnection system that improves the stability and reliability of the entire system by eliminating the above.

In MAC bridging stipulated by IEEE802.1D, etc., when a network is configured by combining a large number of switch nodes, if a loop that continues flooding traffic on the network is configured due to misconfiguration, etc. At various points, normal communication may be hindered and the network may be brought down.
(1) The flooding traffic that rotates in the loop continues to grow until the transmission bandwidth of the network is used up, thereby using up the transfer capacity of the network.
(2) The learning contents of the MAC address learning table are rewritten and destroyed by flooding traffic that rotates in the loop.
(3) The flooding traffic rotating in the loop has an adverse effect on the end node equipment.
Because of this adverse effect, loops should not be generated in MAC bridging networks, and various mechanisms for preventing loops have been considered.

  IEEE802.1D STP (Spanning Tree Protocol) is a typical mechanism for maintaining the topology so that loops are not formed. In many cases, a protocol that maintains such a topology controls the logical configuration of a network so that a loop is not formed by setting a specific interface to a non-forwarding state. However, even when a mechanism such as STP is used, a loop may not be automatically eliminated due to an overload or abnormality of the CPU. For this reason, in the unlikely event that a loop occurs, a means to eliminate the generated loop is prepared, the occurrence of the loop is detected, and the location of the loop (the occurrence of the loop) It is necessary to find out the location.

  For the occurrence of a loop, a method for checking the frequency of rewriting the MAC address learned in the learning table on the MAC bridging device, periodically sending a multicast frame for loop detection to the network, etc., and it does not return This can be detected by a method of checking whether or not the flow rate of flooding traffic flowing on the network and a pattern change are observed.

  In the extended MAC bridging method, a TTL (Time To Live) field that holds integer frame lifetime information (TTL) is provided in a frame to be transmitted, and every time the frame passes through a switch node. A method of subtracting a predetermined value from a TTL and discarding the frame when a predetermined value, for example, a frame holding a TTL of “0” is received, and warning of the possibility of a loop by Trap or Syslog There is also. The occurrence of a loop can be detected by these methods.

  On the other hand, with regard to detection of a loop occurrence location, a method of directly detecting a switch node in which a loop has occurred using TTL has been proposed as described in, for example, Patent Document 1 below. However, the detection of the loop occurrence location using TTL is used in the network core of a telecommunications carrier that provides wide-area Ethernet, but from the Ethernet used in general LAN and the switch of the carrier in wide-area Ethernet, In the Ethernet of the access line part to the subscriber's home, MAC bridging using TTL is not used because it is not a standard MAC bridging protocol. In other words, loop location detection using TTL detects loop occurrence locations on the access line from the operator's switch to the subscriber's home, and connects the subscriber's home LAN and wide-area Ethernet network with a MAC bridging device. It cannot be used to determine the location of a loop occurrence in the subscriber's home when it is used.

  In the wide area Ethernet, if a loop occurs in the access section to the subscriber's home or in the LAN in the subscriber's home, the loop somewhere in the Ethernet segment is monitored by monitoring the frequency of rewriting the MAC address of the operator's switch. It can be detected in a short time to detect the situation where the error occurs. In addition, when a subscriber has multiple bases, it is possible to determine which base a loop has occurred by finding a port with a large amount of traffic inflow and closing the corresponding port to eliminate the influence of the loop. The method of confirming is mainly performed. However, this method has the risk of blocking access that does not actually cause a loop, and it takes a long time to search manually by the time of discovery. There is a problem of end.

  In addition, when a multicast or broadcast frame is periodically transmitted from each port of the operator's switch accommodating the access line and the frame is returned to the transmitting switch, a loop occurs. Although it is possible to determine the base and access line of a subscriber, a special dedicated switch is required, and it may not be economically available.

Further, as another method, for example, there is a “cable modem system” described in Patent Document 2 below, and after the loop detection packet is transmitted from the center device, the loop detection packet is supplied from the subscriber's home side. In this case, the bridge (cable modem) itself has a role to make a judgment by paying attention to the destination address supplied from the inside of the subscriber's house. It was necessary and could not be used with equipment using a general-purpose bridge system.
JP 2005-328164 A JP 2000-183943 A

  As described above, in order to detect the location of the loop, a multicast or broadcast frame is periodically transmitted from each port of the operator's switch accommodating the access line, and the switch returns to the switch that transmitted the frame. In the method of confirming the coming, a special dedicated switch is required, and there is a problem that it may not be economically available. In addition, the method of Patent Document 2 requires dedicated mounting on the bridge (cable modem) itself. Therefore, there is a problem that it cannot be used in equipment using a general-purpose bridge system.

  The object of the present invention is to solve the above-mentioned problem, and in a MAC bridging network (LAN or wide area Ethernet (registered trademark)), it is possible to easily and quickly and economically determine in which direction of the network a loop occurs. An object of the present invention is to provide a loop generation direction determination method that can be detected and helps to eliminate communication troubles, and a loop disconnection method that disconnects a loop network using the determination method.

  In order to achieve the above-described object, the present invention provides a test apparatus for sending a test frame for inspecting the presence or absence of loop generation to the MAC bridging network in a loop generation direction determination method on the MAC bridging network. A plurality of MACs located on the MAC bridging network, receiving the test frame, learning the source address and the received physical or logical port in a learning table, and then transferring the MAC according to the destination of the test frame A bridging device, and a loop generation direction determination device triggered when the test frame returns to the test device, wherein the loop generation direction determination device determines the loop generation direction by examining the learning table There is a first feature in the point of doing so.

  Further, the loop generation direction determination device, when the source MAC address of the test frame is learned in a port that is not logically closest to the test device when viewed from the MAC bridging device, A second feature is that it is determined that there is a loop in the direction.

  In addition, the loop occurrence direction determining device may perform the MAC bridging before the contents of the source MAC address of the test frame are erased and before the next test frame is transmitted from the test device. Thirdly, by checking the learning table of the device a plurality of times, even if the MAC bridging device itself forms a loop, the port forming the loop can be detected. There are features.

  In addition, a means for blocking a port of the MAC bridging device located on the MAC bridging network is provided, and when the occurrence of a loop is detected by the loop occurrence direction determination method, the port of the MAC bridging device is automatically set. There is a fourth feature in that it is closed.

  According to the first feature of the present invention, in a MAC bridging network, by using a conventional learning table, it is possible to easily and quickly determine the direction of occurrence of a loop, and to help eliminate communication troubles. Can do.

  Further, according to the second feature, it is possible to easily and quickly determine the direction of occurrence of a loop only by examining the learning status of the Port in the learning table.

  Further, according to the third feature, even when the MAC bridging device as a node itself forms a loop, the port forming the loop can be detected.

  Further, according to the fourth feature, when the occurrence of a loop is detected, the loop of the MAC bridging device in the direction of occurrence of the loop is automatically blocked to disconnect the loop from the MAC bridging network. Can do. As a result, the problems (1) to (3) described in the background art can be quickly resolved.

  First, the outline of the present invention will be described. In the present invention, a test apparatus that transmits multicast or broadcast is connected to the Ethernet for which the loop occurrence direction determination is to be performed. When one test frame is transmitted from the test apparatus as a test multicast or broadcast, when a loop has occurred, it can be observed that the test frame returns to the test apparatus that has transmitted the loop. Since the occurrence of the loop itself can be detected as a result, the determination of the direction of occurrence of the loop is started using this as a trigger.

  At this time, on the learning table of the MAC bridging device on Ethernet (core switch CSW, edge switch ESW, etc., which will be described later), the source address of the test frame is a port that is not in the test device direction as seen from the MAC bridging device logical configuration If it is learned, it can be determined that a loop has occurred in the connection destination direction of the port. If you suspect that the MAC bridging device itself forms a loop, check the learning table multiple times, even if the node itself forms a loop. The occurrence of a situation where the address is learned in a port that is not logically closest to the test device when viewed from the MAC bridging device can be detected with high probability.

  If a loop has not occurred, the test frame does not return to the test device, and the source address of the test frame is logically in the direction in which the test device exists logically in the learning table of all MAC bridging devices in the Ethernet segment. It will be learned at the port. Note that if the learning table of the MAC bridging device is not newly re-learned, the learning contents are erased after a certain period of time, so the MAC address of the transmission source of the test frame is learned on the learning table after transmitting the test frame. Therefore, it is necessary to examine the contents of the learning table before the disappearance occurs (generally within 5 minutes).

  If you want to centrally detect the occurrence of the loop and detect the direction, it is assumed that the loop has occurred when the test frame is periodically transmitted and the test frame returns to the test equipment by the loop, and the test frame is temporarily transmitted. The loop generation and direction determination can be performed centrally by determining the loop generation direction according to the learning table status of the MAC bridging device at that time.

  In addition, if a loop occurs in the direction of a specific port of MAC bridging in advance or if it is determined that the loop is a port that constitutes the loop itself, by constructing a system to automatically disconnect the port, A network that is automatically looped when a loop occurs can be disconnected while protecting a specific area of the network.

  Embodiments of the present invention will be described below in detail with reference to the drawings. The present invention is directed to a general MAC bridging network having a MAC address learning function. The MAC address learning table is described in detail in a patent application filed by the present inventor (for example, Japanese Patent Application Laid-Open No. 2004-304230), and further description thereof will be omitted. MAC) for registering a MAC) and at least a Port registration area for registering a physical or logical port on which a frame has arrived.

  FIG. 1 is a block diagram showing an example of a MAC bridging network (Ethernet) to which the present invention is applied. The LAN of this example is an edge switch (hereinafter referred to as ESW) that accommodates direct access and performs MAC bridging. 1) and a MAC bridging network 5 having a core switch (hereinafter referred to as CSW) 4 that performs MAC bridging without accommodating direct access, and transmits a loop test frame to the CSW 4, Is connected to a test apparatus 6 that performs generation and direction determination. The ESWs 1, 2, and 3 are connected to respective access units and terminal bases A, B, and C.

  With reference to FIG. 1, the flow of the test frame in a state where no loop has occurred will be described. As shown in the table T6, the test frame a output from the test apparatus 6 has an address “α” unique to the test apparatus 6 as a source address, and a multicast address, broadcast address, Or it has a flooded address such as an unknown unicast address.

  When the test frame a is transmitted from the test apparatus 6, the test frame a arrives at the CSW 4. Thus, it is learned that the address “α” exists in the direction of “Port (1)” from which the test frame is sent in the learning table T4 of CSW4.

  Next, in FIG. 2, the test frame a has a multicast or broadcast address as a destination address and is flooded. Therefore, the test frame a is simultaneously copied and transferred from CSW4 to ESW1, ESW2, and ESW3. In the learning tables T1, T2, and T3, it is learned that the address “α” exists in the direction of “Port (1)” from which the test frame a is sent.

  As shown in FIGS. 1 and 2, the learning tables T1 to T4 of each MAC bridging device are logical when the source address “α” of the test frame a is viewed from the MAC bridging device in a situation where no loop occurs. It can be seen that learning is performed in the port direction closest to the test apparatus 6.

  FIG. 3 shows that when a loop R occurs at the terminal base B, the test frame a is returned from the terminal base B and returned to “Port (2)” of the ESW2. As a result of this folding, in the learning table T2 of ESW2, rewriting learning is performed assuming that the address “α” unique to the test apparatus 6 is on the “Port (2)” side of ESW2. Note that “x” in the learning table T2 indicates that rewriting learning has been performed. The same applies to the learning tables in the subsequent figures.

  Further, FIG. 4 shows a state in which the returned test frame a returns to “Port (3)” of CSW4. As a result, in the learning table T4 of CSW4, an address “unique to the test apparatus 6” is shown. Rewriting learning is performed on the assumption that “α” is on the “Port (3)” side of CSW4.

  Further, in FIG. 5, the test frame a turned back by the loop R branches from the CSW 4 and is sent to the test apparatus 6, ESW 1, ESW 3. Since ESW1 and ESW3 receive the loopback test frame a from each “Port (1)”, the state in which “α” is learned on the “Port (1)” side does not change (that is, rewriting does not occur). . On the other hand, the test apparatus 6 determines that a loop has occurred in the MAC bridging network 5 because the test frame has been sent back at this time, and uses this determination as a trigger to check the direction of occurrence of the loop.

  Specifically, in the MAC bridging device learning tables T <b> 1 to T <b> 4 on the MAC bridging network 5, the address “α” unique to the test device 6 is learned at the port logically closest to the test device 6. Investigate whether or not it is present. This check is performed by a mechanism (generally, remote login by SNMP or a program) that reads information in the learning table of the MAC bridging device by a device independent of the MAC bridging device (for example, the test device 6). The check may be performed by a device other than the test device.

  When the learning status of the transmission source MAC address of the frame transmitted from the test device 6 in each MAC bridging device is confirmed in FIG. 5, it is confirmed that ESW1 and ESW3 are learning in the direction in which the test device 6 is connected. I understand. On the other hand, in CSW4 and ESW2, learning is performed in a direction other than the direction in which the test apparatus 6 is connected, so that the loop R in the direction of Port (3) as viewed from CSW4 and in the direction of Port (2) as viewed from ESW2 Is determined to have occurred. From the connection configuration of the MAC bridging device and this learning situation, it can be seen that as a result, the loop R occurs in the LAN of the terminal base B or the access portion to the terminal base B.

  If it is determined in advance that the loop is in the port direction for the terminal bases of ESW1, ESW2, and ESW3, the port (2) direction (terminal) as viewed from ESW2 is set by automatically or manually closing the port. If it is determined that a loop has occurred in the base), the port in the direction of the terminal base B of ESW2 is automatically blocked, and the loop R is disconnected, so that the entire network is affected by the loop. It can be prevented.

  FIG. 6 shows a case where a loop occurs in a manner different from the above. As shown in FIG. 6, when considering the case where the target node itself for determining the loop occurrence direction, that is, the MAC bridging device itself, forms a part of the loop, the test frame returned from the access part In “a1” and “a2”, “α” is learned on the “Port (2)” side by ESW1 and ESW2, respectively (see learning tables T1 and T2).

  FIG. 7 shows a case where the folded test frames a1 and a2 have arrived at CSW4. As shown in the figure, in the learning table T4 of CSW4, the folded frames a1 and a2 are overwritten and learned with “α” in the direction of “Port (2)” or “Port (3)”. Which is overwritten depends on which frame arrived later.

  Further, FIG. 8 shows a case where the folded test frames a1 and a2 are sent to the test apparatus 6, ESW1, ESW2, and ESW3. As shown in the drawing, the learning table T3 is not overwritten in the ESW3 that does not form a loop, but “α” on the “Port (1)” side in the learning tables T1 and T2 of the ESW1 and ESW2 that form the loop. If this exists, rewriting of learning occurs. The test apparatus 6 determines that a loop has occurred because the test frame a has arrived, and uses this determination as a trigger to examine the direction of loop generation.

  Specifically, the contents of the learning tables T1 to T4 of each MAC bridging device are confirmed. In this case, since the test frame a continues to rotate between ESW1, ESW2, and CSW4, the learning table T4 of CSW4 loops. Because of this, “α” is always learned in the direction of “Port (2)” or “Port (3)”. For this reason, it is determined that there is a loop in either the “Port (2)” or “Port (3)” direction. (If a multiple confirmation method described later is used, it is possible to determine that “Port (2)” and “Port (3)” constitute a loop.)

  On the other hand, whether “α” is learned in “Port (1)” or “Port (2)” in the learning tables T1 and T2 of ESW1 and ESW2 depends on the timing of reading the learning table of the MAC bridging device. Therefore, there is a case where it is not possible to determine which direction the loop is generated by reading the learning table once. However, since rewriting always occurs, the number of times considered to be sufficient for the determination at an appropriate time interval (this time interval and the number of times may be determined in advance, or MAC learning after the test device detects a loop) (You may decide taking into account the time to erase the contents of the table), by reading the learning tables T1 and T2, "α" has been learned in "Port (2)" with a certain probability Can be confirmed.

  That is, according to the present embodiment, before the disappearance of the contents of the source address of the test frame learned in the learning table of the MAC bridging device occurs (generally within 5 minutes) and the next test By checking the learning table of the MAC bridging device multiple times before the frame is transmitted from the test device, even if the node, that is, the MAC bridging device itself forms a loop, the test frame A port forming a loop of the node by detecting the occurrence of a situation in which the source MAC address is learned in a port that is not logically closest to the test device when viewed from the MAC bridging device Can be detected.

  If the purpose is to eliminate the loop, a loop occurred in advance in the port direction for the terminal bases A, B, and C of ESW1, ESW2, and ESW3 (that is, the test frame in the direction of “Port (2)”) If it is determined that the source address has been learned), the terminal bases A, B, and C are automatically viewed from ESW1, ESW2, and ESW3 by automatically or manually closing the port. Direction port is blocked. As a result, the loop is disconnected, and it is possible to prevent the loop from affecting the entire network.

  When the MAC bridging device itself that determines the loop direction is part of the loop, the port that is logically closest to the test device as viewed from the MAC bridging device forms a loop. If you want to detect the test frame, the source MAC address of the test frame is detected in a port that is not logically closest to the test device when viewed from the MAC bridging device. Later, the learning table of the MAC bridging device is confirmed multiple times. Then, depending on the detection timing, a situation where the source MAC address of the test frame is learned in the port direction logically closest to the test device when viewed from the MAC bridging device is also detected, but the test is performed on the learning table. The loop can be detected by detecting the learning status of the MAC address of the frame transmission source before the occurrence of the cancellation. In this way, since the part related to the occurrence of the loop can be specified, it can be used to remove the influence of the loop.

It is a block block diagram which shows an example of the MAC bridging network (Ethernet) to which this invention is applied, and is a figure which shows a state when a test frame is transmitted from a test apparatus. It is a figure which shows the state of the test frame and the learning table in the state where the loop has not generate | occur | produced. It is a figure which shows the state which the loop generate | occur | produced in the terminal base B, and the state of a learning table. It is a figure which shows the flow of the test frame which reaches | attains CSW when a loop generate | occur | produces in the terminal base B, and the state of a learning table. It is a figure which shows the flow of the final test frame when a loop generate | occur | produces in the terminal base B, and the state of a learning table. It is a figure which shows the state where a test frame is sent to ESW from an access part, and the state of a learning table in case the MAC bridging apparatus itself of which the loop generation direction is determined forms part of the loop. It is a figure which shows the state in which a test frame is sent from CSW to CSW, and the state of a learning table in case the MAC bridging apparatus itself of which the loop generation direction is determined constitutes a part of the loop. It is a figure which shows the state of the test frame sent from CSW to ESW, a test device, and the state of a learning table when the MAC bridging device itself that determines the direction of occurrence of the loop constitutes a part of the loop.

Explanation of symbols

  1, 2, 3 ... Edge switch (ESW), 4 ... Core switch (CSW), 5 ... MAC bridging network, 6 ... Test device, T1-T4 ... Learning table.

Claims (8)

In the loop direction determination method on the MAC bridging network,
A test device that sends a test frame to the MAC bridging network to check whether a loop has occurred,
A plurality of MAC bridges that are located on the MAC bridging network, receive the test frame, learn a transmission source address and the received physical or logical port in a learning table, and then transfer them according to the destination of the test frame A device,
A loop occurrence direction determination device triggered when the test frame returns to the test device;
The loop generation direction determination apparatus, wherein the loop generation direction determination apparatus determines the generation direction of a loop by examining the learning table. In the loop occurrence direction determination method according to claim 1,
A loop occurrence direction determination method, wherein the destination of the test frame is a destination that is flooded and transferred on the MAC bridging network, such as a multicast address, a broadcast address, an unknown unicast address, or the like. In the loop occurrence direction determination method according to claim 1 or 2,
A loop generation direction determination method, wherein the test apparatus also serves as the loop generation direction determination apparatus. In the loop occurrence direction determination method according to any one of claims 1 to 3,
The learning table has at least a source MAC address registration area and a Port registration area for registering a physical or logical port where the frame arrived, and the loop occurrence direction determination device is configured to transmit the test frame source MAC Loop generation direction determination characterized by determining that there is a loop in the direction when the address is learned in a port that is not logically closest to the test apparatus when viewed from the MAC bridging apparatus method. In the loop occurrence direction determination method according to any one of claims 1 to 4,
The test apparatus transmits the test frame periodically, and determines a loop occurrence direction. In the loop occurrence direction determination method according to claim 5,
The loop generation direction judging device is a learning table of each MAC bridging device before the content of the source MAC address of the test frame is erased and before the next test frame is transmitted from the test device. Loop direction determination method characterized by checking In the loop occurrence direction determination method according to claim 6,
The loop occurrence direction determination device is configured to perform the process before each of the MAC bridging devices before the deletion of the content of the transmission source MAC address of the test frame and before the next test frame is transmitted from the test device. By confirming the learning table multiple times, even if the MAC bridging device itself forms a loop, the port that forms the loop can be detected as the loop generation direction. Loop generation direction determination method characterized by Comprising means for blocking a port of a MAC bridging device located on the MAC bridging network;
8. A loop disconnection system characterized in that when a loop occurrence is detected by the loop generation direction determination system according to any one of claims 1 to 7, the port of the MAC bridging device is automatically closed. .

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