CA2477070A1 - Local network, particularly ethernet network having redundancy properties, and redundancy manager for such a network - Google Patents
Local network, particularly ethernet network having redundancy properties, and redundancy manager for such a network Download PDFInfo
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- 230000008878 coupling Effects 0.000 claims abstract description 47
- 238000010168 coupling process Methods 0.000 claims abstract description 47
- 238000005859 coupling reaction Methods 0.000 claims abstract description 47
- 238000012360 testing method Methods 0.000 claims abstract description 24
- 238000013101 initial test Methods 0.000 claims abstract description 17
- 238000012544 monitoring process Methods 0.000 description 9
- 238000004891 communication Methods 0.000 description 6
- 239000000835 fiber Substances 0.000 description 6
- 230000005540 biological transmission Effects 0.000 description 5
- 230000007257 malfunction Effects 0.000 description 3
- 238000012937 correction Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- 230000011664 signaling Effects 0.000 description 1
- 230000001960 triggered effect Effects 0.000 description 1
Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
- H04L69/40—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass for recovering from a failure of a protocol instance or entity, e.g. service redundancy protocols, protocol state redundancy or protocol service redirection
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/22—Arrangements for detecting or preventing errors in the information received using redundant apparatus to increase reliability
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L12/40169—Flexible bus arrangements
- H04L12/40176—Flexible bus arrangements involving redundancy
- H04L12/40182—Flexible bus arrangements involving redundancy by using a plurality of communication lines
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L12/403—Bus networks with centralised control, e.g. polling
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/42—Loop networks
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/42—Loop networks
- H04L12/423—Loop networks with centralised control, e.g. polling
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/42—Loop networks
- H04L12/437—Ring fault isolation or reconfiguration
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L43/00—Arrangements for monitoring or testing data switching networks
- H04L43/50—Testing arrangements
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Computer Security & Cryptography (AREA)
- Small-Scale Networks (AREA)
- Computer And Data Communications (AREA)
Abstract
The invention relates to a local network, particularly an Ethernet network having redundancy properties, in which coupling devices (K1, K2, K3) and a redundancy manager (RM) are interconnected in a ring-shaped topology. The redundancy manager opens the ring to create a linear topology if test messages (T11, T12) emitted by said redundancy manager (RM) are received at the other port (P42, P41) within a given period of time, otherwise the redundancy manager (RM) closes the connection. As a so-called redundancy manager observer, at least one of the coupling devices (K3) is configured such that it evaluates messages received at the port (P32) thereof, said port (P32) being connected to the redundancy manager, opens the ring to create a linear topology, and signals an error if more than initial test messages (T11) have been received at said port (P32) and if the status ring opened has been indicated by the redundancy manager (RM) in the last-received initial test message (T11), whereby messages are prevented from circulating on the ring.
Description
LOCAL NETWORK, PARTICULARLY ETHERNET NETWORK HAVING
REDUNDANCY PROPERTIES, AND REDUNDANCY MANAGER FOR
SUCH A NETWORK
Description Local network, particularly Ethernet network, having redundancy properties and coupling device for such a network The invention relates to a local network, particularly an Ethernet network having redundancy properties in accordance with the preamble of Claim 1 and a coupling device for such a network in accordance with the preamble of Claim 6.
A local Ethernet network with redundancy properties is known from WO
99/46908. In the network described therein, coupling devices and a redundancy manager, each having at least two ports and being configured as layer 2 components, are interconnected in a ring-shaped topology by connecting two ports of adjacent devices. The term "layer 2 components" means that at least the layers 1 and 2 of the ISO OSI 7-layer model are implemented in the devices.
The devices thus perform an address evaluation and message routing. In normal operation, i.e., if no errors have occurred in the network, the redundancy manager opens the ring. This means that messages received by the redundancy manager at its one port located in the ring are not forwarded via its other port located in the ring, but are blocked. This status is symbolized by an open switch. Thus, logically, the network has a linear topology in which the two line ends of the network are connected to a redundancy manager, which in the error-free case separates the two line ends from one another. In the event of an error, i.e., if an interruption occurs at some point in the network outside the redundancy manager, the redundancy manager connects the two line ends to again form a linear topology.
Physically, however, this is a ring-shaped network topology in which the devices form a ring by connecting two ports of adjacent devices. The redundancy manager ensures that at any given time the ring is interrupted only at a single location. To check whether there is already an interruption of the ring outside the redundancy manager, i.e., to check whether the network is operating error free, the redundancy manager sends test messages into the ring at defined time intervals via the two ports with which it is connected to the ring, and it opens the ring to form a linear topology with respect to the transmission logic if the test messages are received at its other port within an additional predefined time interval.
Otherwise, i.e., if at least one test message has been received at the other port within the additional time interval, the redundancy manager closes the connection, such that the network has again a logically linear topology consisting of a continuous line. With respect to further embodiments and advantages of such a local network and a redundancy manager, reference is made to the above-cited publication WO 99/4690$.
Networks in which messages are distributed from node to node and in which the response to the failure of a communication link between two nodes is to add a redundant communication path, have the risk that messages are copied or circulate within the network. Such errors can be triggered when a redundant communication path is mistakenly added. Thus, as a result of a malfunction of the conventional redundancy manager, the two line ends could inadvertently be connected and a logically ring-shaped network topology could be created. As a result messages can circulate within the ring. In the worst case, the maximum bandwidth of the network available for the data traffic is occupied, such that further payload traffic among the users connected to the network can no longer be transmitted. When such an error occurs, the network is not or not fully available for the connected users.
One object of the invention is to provide a local network, particularly an Ethernet network having redundancy properties, which is distinguished by an increased availability of the network for the transmission of payload data of the connected users. A further object is to provide a coupling device to attain this object in a network.
To attain these objects, the novel local network of the initially described type has the features set forth in the characterizing portion of Claim 1. Advantageous further refinements of the invention are described in the dependent claims. A
coupling device for such a network is described in Claim 6.
The invention has the advantage that the monitoring for the correct functioning of the redundancy manager is independent of the redundancy manager. Thus, errors within the redundancy manager cannot interfere with the monitoring or make it impossible. Any accidental closing of the network connection by the redundancy manager is quickly detected by the so-called redundancy manager observer. Any en ors that occur are corrected by opening the ring without relatively long delays.
This increases the availability of the local network. In addition, any errors during startup, e.g., an incorrect configuration of the redundancy manager, are detected.
REDUNDANCY PROPERTIES, AND REDUNDANCY MANAGER FOR
SUCH A NETWORK
Description Local network, particularly Ethernet network, having redundancy properties and coupling device for such a network The invention relates to a local network, particularly an Ethernet network having redundancy properties in accordance with the preamble of Claim 1 and a coupling device for such a network in accordance with the preamble of Claim 6.
A local Ethernet network with redundancy properties is known from WO
99/46908. In the network described therein, coupling devices and a redundancy manager, each having at least two ports and being configured as layer 2 components, are interconnected in a ring-shaped topology by connecting two ports of adjacent devices. The term "layer 2 components" means that at least the layers 1 and 2 of the ISO OSI 7-layer model are implemented in the devices.
The devices thus perform an address evaluation and message routing. In normal operation, i.e., if no errors have occurred in the network, the redundancy manager opens the ring. This means that messages received by the redundancy manager at its one port located in the ring are not forwarded via its other port located in the ring, but are blocked. This status is symbolized by an open switch. Thus, logically, the network has a linear topology in which the two line ends of the network are connected to a redundancy manager, which in the error-free case separates the two line ends from one another. In the event of an error, i.e., if an interruption occurs at some point in the network outside the redundancy manager, the redundancy manager connects the two line ends to again form a linear topology.
Physically, however, this is a ring-shaped network topology in which the devices form a ring by connecting two ports of adjacent devices. The redundancy manager ensures that at any given time the ring is interrupted only at a single location. To check whether there is already an interruption of the ring outside the redundancy manager, i.e., to check whether the network is operating error free, the redundancy manager sends test messages into the ring at defined time intervals via the two ports with which it is connected to the ring, and it opens the ring to form a linear topology with respect to the transmission logic if the test messages are received at its other port within an additional predefined time interval.
Otherwise, i.e., if at least one test message has been received at the other port within the additional time interval, the redundancy manager closes the connection, such that the network has again a logically linear topology consisting of a continuous line. With respect to further embodiments and advantages of such a local network and a redundancy manager, reference is made to the above-cited publication WO 99/4690$.
Networks in which messages are distributed from node to node and in which the response to the failure of a communication link between two nodes is to add a redundant communication path, have the risk that messages are copied or circulate within the network. Such errors can be triggered when a redundant communication path is mistakenly added. Thus, as a result of a malfunction of the conventional redundancy manager, the two line ends could inadvertently be connected and a logically ring-shaped network topology could be created. As a result messages can circulate within the ring. In the worst case, the maximum bandwidth of the network available for the data traffic is occupied, such that further payload traffic among the users connected to the network can no longer be transmitted. When such an error occurs, the network is not or not fully available for the connected users.
One object of the invention is to provide a local network, particularly an Ethernet network having redundancy properties, which is distinguished by an increased availability of the network for the transmission of payload data of the connected users. A further object is to provide a coupling device to attain this object in a network.
To attain these objects, the novel local network of the initially described type has the features set forth in the characterizing portion of Claim 1. Advantageous further refinements of the invention are described in the dependent claims. A
coupling device for such a network is described in Claim 6.
The invention has the advantage that the monitoring for the correct functioning of the redundancy manager is independent of the redundancy manager. Thus, errors within the redundancy manager cannot interfere with the monitoring or make it impossible. Any accidental closing of the network connection by the redundancy manager is quickly detected by the so-called redundancy manager observer. Any en ors that occur are corrected by opening the ring without relatively long delays.
This increases the availability of the local network. In addition, any errors during startup, e.g., an incorrect configuration of the redundancy manager, are detected.
A signaling of such an error by the redundancy manager observer has the advantage that suitable error correction measures can be taken, e.g., the redundancy manager can be repaired or replaced.
The monitoring principle has the advantage of managing without additional test messages that burden the network. In the initial test messages, the redundancy manager indicates the corresponding status "ring opened" or "connection closed"
and a coupling device, which is adjacent to the redundancy manager in the ring, opens the ring if more than only initial test messages are received at the port to which the redundancy manager is connected and the redundancy manager has indicated the status "ring opened" in the last received of the initial test messages.
This monitoring principle can advantageously be supplemented by the monitoring of the redundancy manager by the redundancy manager observer using its own second test messages to further reduce the failure probability of the network.
In the normal case, i.e., in error-free operation, the redundancy manager observer transparently forwards initial test messages of the redundancy manager and takes second test messages, which the redundancy manager observer has fed into the ring, off the ring when it receives them, i.e., it does not forward them.
Correspondingly, the redundancy manager transparently forwards second test messages if the redundancy manager has closed the connection. The redundancy manager blocks second test massages, however, i.e., it does not forward them, if the redundancy manager has opened the ring. Configuring the second test messages differently from the initial test messages has the advantage that these functions of the redundancy manager and the redundancy manager observer can be correspondingly executed immediately after the respective message type has been detected. This eliminates the need for a complex matching of the instants of transmission of the initial and the second test messages between the redundancy manager and the redundancy manager observer and a distinction based on the time position of the test messages, which could be an alternative to the distinction by message types based on the messages themselves.
Advantageously, the failure probability is further reduced if all the coupling devices interconnected in the ring-shaped topology are configured as redundancy manager observers. This also ensures a monitoring of the functioning of a redundancy manager observer by the other redundancy manager observers. For this purpose, the redundancy manager observers can use a protocol among each other to determine the valid network topology. In the simplest case, however, an exchange of synchronization messages among the redundancy manager observers is sufficient.
The invention and its embodiments and advantages will now be explained in greater detail with reference to the drawing, which depicts an exemplary embodiment of the invention.
In a network, four coupling devices K1, K2, K3 and RM are interconnected, and the coupling device RM is operated as a redundancy manager. The coupling devices each have four ports P11...P14, P21...P24, P31...P34 and P41...P44 to which connecting lines for the reception and transmission of messages can be connected. The coupling devices K1 to K3 and RM are configured as layer 2 components, i.e., they route messages in accordance with an internally stored address table. They are interconnected into a ring-shaped topology such that two ports of adjacent devices are connected. For this purpose, the ports P12 and are interconnected by fibers F12 and F21 of a glass fiber cable. Copper cable can of course be used as an alternative. The fiber F12 serves to transmit messages from port P12 of the coupling device K1 to the port P21 of the coupling device K2. In the opposite direction, messages are transmitted from the port P21 of the coupling device K2 to the port P12 of the coupling device K1 via the fiber F21.
Thus, a so-called full duplex transmission is possible, in which messages can be simultaneously transmitted in both directions. Correspondingly, the ports P22 and P31 are interconnected by fibers F23 and F32, the ports P32 and P41 by fibers F34 and F43 and the ports P42 and P11 by fibers F41 and F14. A user TN1 is connected to the port P13 of the coupling device K1, a user TN2 to the port of the coupling device K2, a user TN3 to the port P24 of the coupling device K2, a user TN4 to the port P34 of the coupling device K3 and a user TNS to the port P44 of the coupling device RM. These users can be, for example, automation devices, control and monitoring stations, servers, printers, other network segments, etc.
Logically, during error-free operation, the network is a local network with a linear topology, since the ring is interrupted at the coupling device RM, which is operated as the redundancy manager. This interruption is indicated by a switch S4. Corresponding switches S1, S2 and S3 in the coupling devices K1, K2 and K3 are closed. A closed switch S1 of the coupling device K1, for example, means that the messages to be switched through by the coupling device K1 in the line are transparently switched from the receive port, e.g., the port P11, to the send port, e.g., the port P12. The same is true in opposite direction. In the event of an error, i.e., if the depicted line is interrupted, the redundancy manager connects the two line ends together, i.e., it forwards the messages received at the port P41 via the port P42 and vice versa if they must be switched through and are not addressed to the user TNS. This corresponds to a switch S4 in closed position. To monitor the line for possible interruptions, the redundancy manager RM sends initial test messages T11 and T12 into the ring at first predefined intervals via the two ports P41 and P42 with which it is connected to the ring. If these initial messages and T12 are received at the other port P42 or P41 within a second predefined time interval, the line is not interrupted and the ring is opened to create or-depending on the previous status-maintain a linear topology, i.e., the switch S4 is or remains opened. If the initial test messages T11 or T12 are not received at the other port P42 or P41 within the second time interval, an error is present and the line is interrupted. The error is thus detected and the switch S4 is closed, such that a functioning line is restored and communication continues to be ensured. When defining the first and second time intervals, the maximum circulation time of messages within the network and the maximum allowable reconfiguration time must be taken into account. If the time intervals are suitably selected this reconfiguration of the network is comparatively fast, which ensures that the connected users do not dismantle any logic communication connections, that communication continues without interruptions and that any automation solution realized by means of the network remains unaffected.
If the redundancy manager RM closed the switch S4 due to an internal error without an interruption having occurred in the rest of the ring, then circulating messages could be created in the ring. This would be the case, for example, if the software of the redundancy manager RM incorrectly switched messages through because of a software or logic error even though there was no interruption in the rest of the ring. Such errors could affect the availability of the network. To prevent this, the coupling device K3, for example, is operated as a so-called redundancy manager observer. All the coupling devices in the embodiment shown, including the coupling devices K1 and K2 could be operated analogously.
However, the description with reference to the coupling device K3 is sufficient to explain the invention. To monitor the redundancy manager RM, the coupling device K3 also sends second test messages T21 and T22 at defined third intervals into the ring via the ports P31 and P32. If the two test messages T21 and T22 do not reach the other port P32 or P31 of the coupling device K3 within a fourth defined time interval, then there is an interruption in the remaining part of the ring. The switch S3 remains closed. If the redundancy manager RM incorrectly closes the ring, the second test messages T21 and T22 reach the port P32 or P31.
As a result, a short circuit of the ring would be detected. In this case the coupling device K3 opens the switch S3 to again form a logically linear network topology overall. The third and fourth time interval can be determined analogously to the selection of the first and the second time interval. After a short reconfiguration time the network is again ready for operation. As described above, the coupling devices K1 and K2 can analogously perform the above-described function of a redundancy manager. This has the advantage that any errors of the coupling device K3 are also detected. The coupling device K3 signals a detected error of the redundancy manager RM by a light emitting diode LED. In response, suitable error correction measures can be introduced. Another means to signal an error is, for example, to send an error message to a central network management station.
The described monitoring of the redundancy manager by a redundancy manager observer also makes it possible to detect errors where the software of the redundancy manager RM detects an error-free operation of the rest of the ring but the hardware of the redundancy manager RM is not behaving properly and incorrectly closes the switch S4. If there are no clear indicators for such errors in the redundancy manager RM itself, the redundancy manager cannot detect the error. Such an error is difficult to avoid completely because even a single bit-error in the complex hardware circuit parts of the redundancy manager RM, which the switch S4 represents here in simplified form, could already lead to such an error.
Such errors can be quickly detected using the following type of monitoring. It is assumed here that the redundancy manager RM indicates the corresponding status in the test messages T11 and T12, for example, "ring opened" or "connection closed." The coupling device K3, which is configured as a redundancy manager observer, evaluates the messages received at its port P32, which connects it directly to the redundancy manager RM. A malfunction of the redundancy manager RM is present if the status "ring opened" is indicated in the test messages T11 and other messages besides the test messages T11 are received at the port P32. If those two conditions are met, the coupling device K3 opens its switch S3 and signals an error of the redundancy manager RM with its light emitting diode LED. When one of the two conditions is no longer met, the coupling device K3 closes its switch S3 again. This makes it possible to check the function of the redundancy manager RM without burdening the network with additional test messages of a redundancy manager observer. In addition, a rapid detection of such errors and a rapid network reconfiguration are achieved.
The redundancy manager observer (coupling device K3) checks the decision of the redundancy manager RM to close the ring by sending two messages T21 and T22. When the redundancy manager observer has received the information from the redundancy manager RM that the latter has closed the ring, but the redundancy manager observer itself receives the second test messages it has sent from its one ring port, e.g., the port P31, at its other ring port, here the port P32, then the redundancy manager observer assumes that the redundancy manager has incorrectly closed the switch S4. In response, the redundancy manager observer 1~
(coupling device K3) opens the ring with its switch S3 and signals the malfunction of the redundancy manager.
The monitoring principle has the advantage of managing without additional test messages that burden the network. In the initial test messages, the redundancy manager indicates the corresponding status "ring opened" or "connection closed"
and a coupling device, which is adjacent to the redundancy manager in the ring, opens the ring if more than only initial test messages are received at the port to which the redundancy manager is connected and the redundancy manager has indicated the status "ring opened" in the last received of the initial test messages.
This monitoring principle can advantageously be supplemented by the monitoring of the redundancy manager by the redundancy manager observer using its own second test messages to further reduce the failure probability of the network.
In the normal case, i.e., in error-free operation, the redundancy manager observer transparently forwards initial test messages of the redundancy manager and takes second test messages, which the redundancy manager observer has fed into the ring, off the ring when it receives them, i.e., it does not forward them.
Correspondingly, the redundancy manager transparently forwards second test messages if the redundancy manager has closed the connection. The redundancy manager blocks second test massages, however, i.e., it does not forward them, if the redundancy manager has opened the ring. Configuring the second test messages differently from the initial test messages has the advantage that these functions of the redundancy manager and the redundancy manager observer can be correspondingly executed immediately after the respective message type has been detected. This eliminates the need for a complex matching of the instants of transmission of the initial and the second test messages between the redundancy manager and the redundancy manager observer and a distinction based on the time position of the test messages, which could be an alternative to the distinction by message types based on the messages themselves.
Advantageously, the failure probability is further reduced if all the coupling devices interconnected in the ring-shaped topology are configured as redundancy manager observers. This also ensures a monitoring of the functioning of a redundancy manager observer by the other redundancy manager observers. For this purpose, the redundancy manager observers can use a protocol among each other to determine the valid network topology. In the simplest case, however, an exchange of synchronization messages among the redundancy manager observers is sufficient.
The invention and its embodiments and advantages will now be explained in greater detail with reference to the drawing, which depicts an exemplary embodiment of the invention.
In a network, four coupling devices K1, K2, K3 and RM are interconnected, and the coupling device RM is operated as a redundancy manager. The coupling devices each have four ports P11...P14, P21...P24, P31...P34 and P41...P44 to which connecting lines for the reception and transmission of messages can be connected. The coupling devices K1 to K3 and RM are configured as layer 2 components, i.e., they route messages in accordance with an internally stored address table. They are interconnected into a ring-shaped topology such that two ports of adjacent devices are connected. For this purpose, the ports P12 and are interconnected by fibers F12 and F21 of a glass fiber cable. Copper cable can of course be used as an alternative. The fiber F12 serves to transmit messages from port P12 of the coupling device K1 to the port P21 of the coupling device K2. In the opposite direction, messages are transmitted from the port P21 of the coupling device K2 to the port P12 of the coupling device K1 via the fiber F21.
Thus, a so-called full duplex transmission is possible, in which messages can be simultaneously transmitted in both directions. Correspondingly, the ports P22 and P31 are interconnected by fibers F23 and F32, the ports P32 and P41 by fibers F34 and F43 and the ports P42 and P11 by fibers F41 and F14. A user TN1 is connected to the port P13 of the coupling device K1, a user TN2 to the port of the coupling device K2, a user TN3 to the port P24 of the coupling device K2, a user TN4 to the port P34 of the coupling device K3 and a user TNS to the port P44 of the coupling device RM. These users can be, for example, automation devices, control and monitoring stations, servers, printers, other network segments, etc.
Logically, during error-free operation, the network is a local network with a linear topology, since the ring is interrupted at the coupling device RM, which is operated as the redundancy manager. This interruption is indicated by a switch S4. Corresponding switches S1, S2 and S3 in the coupling devices K1, K2 and K3 are closed. A closed switch S1 of the coupling device K1, for example, means that the messages to be switched through by the coupling device K1 in the line are transparently switched from the receive port, e.g., the port P11, to the send port, e.g., the port P12. The same is true in opposite direction. In the event of an error, i.e., if the depicted line is interrupted, the redundancy manager connects the two line ends together, i.e., it forwards the messages received at the port P41 via the port P42 and vice versa if they must be switched through and are not addressed to the user TNS. This corresponds to a switch S4 in closed position. To monitor the line for possible interruptions, the redundancy manager RM sends initial test messages T11 and T12 into the ring at first predefined intervals via the two ports P41 and P42 with which it is connected to the ring. If these initial messages and T12 are received at the other port P42 or P41 within a second predefined time interval, the line is not interrupted and the ring is opened to create or-depending on the previous status-maintain a linear topology, i.e., the switch S4 is or remains opened. If the initial test messages T11 or T12 are not received at the other port P42 or P41 within the second time interval, an error is present and the line is interrupted. The error is thus detected and the switch S4 is closed, such that a functioning line is restored and communication continues to be ensured. When defining the first and second time intervals, the maximum circulation time of messages within the network and the maximum allowable reconfiguration time must be taken into account. If the time intervals are suitably selected this reconfiguration of the network is comparatively fast, which ensures that the connected users do not dismantle any logic communication connections, that communication continues without interruptions and that any automation solution realized by means of the network remains unaffected.
If the redundancy manager RM closed the switch S4 due to an internal error without an interruption having occurred in the rest of the ring, then circulating messages could be created in the ring. This would be the case, for example, if the software of the redundancy manager RM incorrectly switched messages through because of a software or logic error even though there was no interruption in the rest of the ring. Such errors could affect the availability of the network. To prevent this, the coupling device K3, for example, is operated as a so-called redundancy manager observer. All the coupling devices in the embodiment shown, including the coupling devices K1 and K2 could be operated analogously.
However, the description with reference to the coupling device K3 is sufficient to explain the invention. To monitor the redundancy manager RM, the coupling device K3 also sends second test messages T21 and T22 at defined third intervals into the ring via the ports P31 and P32. If the two test messages T21 and T22 do not reach the other port P32 or P31 of the coupling device K3 within a fourth defined time interval, then there is an interruption in the remaining part of the ring. The switch S3 remains closed. If the redundancy manager RM incorrectly closes the ring, the second test messages T21 and T22 reach the port P32 or P31.
As a result, a short circuit of the ring would be detected. In this case the coupling device K3 opens the switch S3 to again form a logically linear network topology overall. The third and fourth time interval can be determined analogously to the selection of the first and the second time interval. After a short reconfiguration time the network is again ready for operation. As described above, the coupling devices K1 and K2 can analogously perform the above-described function of a redundancy manager. This has the advantage that any errors of the coupling device K3 are also detected. The coupling device K3 signals a detected error of the redundancy manager RM by a light emitting diode LED. In response, suitable error correction measures can be introduced. Another means to signal an error is, for example, to send an error message to a central network management station.
The described monitoring of the redundancy manager by a redundancy manager observer also makes it possible to detect errors where the software of the redundancy manager RM detects an error-free operation of the rest of the ring but the hardware of the redundancy manager RM is not behaving properly and incorrectly closes the switch S4. If there are no clear indicators for such errors in the redundancy manager RM itself, the redundancy manager cannot detect the error. Such an error is difficult to avoid completely because even a single bit-error in the complex hardware circuit parts of the redundancy manager RM, which the switch S4 represents here in simplified form, could already lead to such an error.
Such errors can be quickly detected using the following type of monitoring. It is assumed here that the redundancy manager RM indicates the corresponding status in the test messages T11 and T12, for example, "ring opened" or "connection closed." The coupling device K3, which is configured as a redundancy manager observer, evaluates the messages received at its port P32, which connects it directly to the redundancy manager RM. A malfunction of the redundancy manager RM is present if the status "ring opened" is indicated in the test messages T11 and other messages besides the test messages T11 are received at the port P32. If those two conditions are met, the coupling device K3 opens its switch S3 and signals an error of the redundancy manager RM with its light emitting diode LED. When one of the two conditions is no longer met, the coupling device K3 closes its switch S3 again. This makes it possible to check the function of the redundancy manager RM without burdening the network with additional test messages of a redundancy manager observer. In addition, a rapid detection of such errors and a rapid network reconfiguration are achieved.
The redundancy manager observer (coupling device K3) checks the decision of the redundancy manager RM to close the ring by sending two messages T21 and T22. When the redundancy manager observer has received the information from the redundancy manager RM that the latter has closed the ring, but the redundancy manager observer itself receives the second test messages it has sent from its one ring port, e.g., the port P31, at its other ring port, here the port P32, then the redundancy manager observer assumes that the redundancy manager has incorrectly closed the switch S4. In response, the redundancy manager observer 1~
(coupling device K3) opens the ring with its switch S3 and signals the malfunction of the redundancy manager.
Claims (6)
1. Local network, particularly Ethernet network with redundancy properties, in which coupling devices (K1, K2, K3) and a redundancy manager (RM), each of which has at least two ports (P11, P12, P21, P22, P31, P32, P41, P42), are configured as layer 2 components and are interconnected in a ring-shaped topology by the connection of two ports of adjacent devices, wherein the redundancy manager (RM) is configured to send initial test messages (T11, T12) into the ring at predefined intervals via the two ports (P41, P42) with which it is connected to the ring and if the initial test messages (T11, T12) are received at the other port (P42, P41 ) within a predefined time interval, to open the ring to create a linear topology and otherwise to close the connection, characterized in that the redundancy manager (RM) is configured to indicate the corresponding status "ring opened" or "connection closed" in the initial test messages (T11, T12) and at least one of the coupling devices (K3) adjacent to the redundancy manager (RM) in the ring is configured, as a so-called redundancy manager observer, to evaluate messages that it receives at its port (P32) which is connected to the redundancy manager (RM) and to open the ring to create a linear topology if more than only the initial test messages (T11) have been received at this port (P32) and the redundancy manager (RM) has indicated the status "ring opened" in the last received initial test message (T11).
2. Local network as claimed in Claim 1, characterized in that the redundancy manager observer is further configured to signal an error if the said conditions for opening the ring are met.
3. Local network as claimed in Claim 1 or 2, characterized in that at least one of the coupling devices (K1, K2, K3) is configured in turn to send second test messages (T21, T22) to monitor the redundancy manager (RM) into the ring at predefined time intervals via the two ports (P31, P32) with which it is connected to the ring and to open the ring to create a linear topology if the second test messages (T21, T22) are received within a predefined time interval at the other port (P32, P31), and otherwise to close the connection between the ports (P31, P32).
4. Local network as claimed in Claim 3, characterized in that the coupling device (K1, K2, K3) is configured to signal an error of the redundancy manager if a second test message is received.
5. Local network as claimed in Claim 3 or 4, characterized in that the second test messages (T21, T22) differ from the initial test messages (T11, T12).
6. Coupling device for a local network as claimed in any one of the preceding claims, characterized in that, when arranged as the coupling device adjacent to the redundancy manager (RM), it is configured as a so-called redundancy manager observer to evaluate messages which it receives at its port (P32) connected to the redundancy manager (RM) and to open the ring to create a linear topology if more than only initial test messages (T11) have been received at this port (P32) and the status "ring opened" has been indicated by the redundancy manager (RM) in the last received initial test message (T11).
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE10207529.8 | 2002-02-22 | ||
| DE10207529A DE10207529B4 (en) | 2002-02-22 | 2002-02-22 | Local network, in particular an Ethernet network with redundancy properties and a coupling device for such a network |
| PCT/DE2003/000555 WO2003073704A1 (en) | 2002-02-22 | 2003-02-21 | Local network, particularly ethernet network having redundancy properties, and redundancy manager for such a network |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2477070A1 true CA2477070A1 (en) | 2003-09-04 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002477070A Abandoned CA2477070A1 (en) | 2002-02-22 | 2003-02-21 | Local network, particularly ethernet network having redundancy properties, and redundancy manager for such a network |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP1476988B1 (en) |
| CN (1) | CN100574241C (en) |
| AT (1) | ATE304761T1 (en) |
| CA (1) | CA2477070A1 (en) |
| DE (2) | DE10207529B4 (en) |
| WO (1) | WO2003073704A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1722515A1 (en) * | 2005-05-11 | 2006-11-15 | Siemens Aktiengesellschaft | Ring system |
| EP1727313A1 (en) * | 2005-05-25 | 2006-11-29 | Siemens Aktiengesellschaft | Ring network and method for automatic protection switching |
| WO2008037781A1 (en) * | 2006-09-29 | 2008-04-03 | Nokia Siemens Networks Gmbh & Co. Kg | Method for protection switching in ring topologies |
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| EP1687681B1 (en) | 2003-11-27 | 2010-08-18 | Siemens Aktiengesellschaft | Method for operating a network |
| CN100448204C (en) * | 2003-11-27 | 2008-12-31 | 西门子公司 | Method for operating a network |
| CN100438475C (en) * | 2004-09-21 | 2008-11-26 | 华为技术有限公司 | Implementation method of protection exchanging in circular network |
| FR2876522B1 (en) * | 2004-10-07 | 2007-01-05 | Schneider Electric Ind Sas | RING COMMUNICATION DEVICE AND METHOD AND COMMUNICATION NETWORK HAVING SUCH A DEVICE |
| DE102004055330A1 (en) * | 2004-11-16 | 2006-05-24 | Bosch Rexroth Aktiengesellschaft | Method and device for operating a network |
| GB2421669A (en) * | 2004-12-22 | 2006-06-28 | Siemens Ag | Method for restoring a link in a communication ring system |
| US8050183B2 (en) * | 2005-05-06 | 2011-11-01 | Cisco Technology, Inc. | System and method for implementing reflector ports within hierarchical networks |
| FR2887099B1 (en) * | 2005-06-13 | 2007-08-31 | Archean Technologies Soc Par A | INFORMATION FLOW DIFFUSION INSTALLATION |
| CN100401712C (en) * | 2005-10-14 | 2008-07-09 | 杭州华三通信技术有限公司 | Fault treating method for phase switching loop of automatic protection system of Ethernet |
| DE102006004339A1 (en) | 2006-01-30 | 2007-08-02 | Robert Bosch Gmbh | Redundant communication network |
| CN1859411A (en) * | 2006-03-18 | 2006-11-08 | 华为技术有限公司 | Method for detecting communication device link ringback and communication device |
| CN101145981B (en) * | 2006-09-13 | 2011-06-22 | 中兴通讯股份有限公司 | Loop detection and switching method of multi-loop Ethernet |
| CN100508663C (en) * | 2007-01-11 | 2009-07-01 | 华为技术有限公司 | Method and device for realizing the preferential access to REC at the RE beginning end |
| CN100534024C (en) * | 2007-11-26 | 2009-08-26 | 中控科技集团有限公司 | Industry ethernet based fault processing method, system and a switching arrangement |
| CN101778030B (en) * | 2009-12-31 | 2014-06-04 | 中控科技集团有限公司 | Ring network-based communication method and ring network |
| EP2562960A1 (en) * | 2011-08-23 | 2013-02-27 | Siemens Aktiengesellschaft | Redundant data transmission method in a communication network |
| WO2013091711A1 (en) | 2011-12-22 | 2013-06-27 | Siemens Aktiengesellschaft | Method for identifying circling messages in a packet-switched communication network and network component for carrying out the method |
| DE102014201373A1 (en) | 2014-01-27 | 2015-07-30 | Robert Bosch Gmbh | Method for operating a redundant communication network |
| EP3026848A1 (en) | 2014-11-27 | 2016-06-01 | Siemens Aktiengesellschaft | Method for data transmission in a redundantly operable industrial communication network and coupling communication device |
| AT517779B1 (en) | 2015-10-01 | 2021-10-15 | B & R Ind Automation Gmbh | Method for cross-traffic between two slaves in a ring-shaped data network |
| DE102015225046A1 (en) | 2015-12-14 | 2017-06-14 | Robert Bosch Gmbh | Method for operating a communication network |
| EP3787237B1 (en) | 2019-08-30 | 2023-04-19 | Siemens Aktiengesellschaft | Method for data transmission in a redundantly operable communication network and coupling communication device |
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| DE3919962C3 (en) * | 1989-06-19 | 1994-07-14 | Hirschmann Richard Gmbh Co | Method and arrangement for securing data transmission in a linear computer network |
| CH688215A5 (en) * | 1994-03-02 | 1997-06-13 | Cerberus Ag | Communication network having a plurality of stations and method of operation. |
| DE19810587A1 (en) * | 1998-03-11 | 1999-09-16 | Siemens Ag | Ethernet (RTM) network with redundancy characteristics |
| US20010052084A1 (en) * | 1998-11-10 | 2001-12-13 | Jiandoug Huang | Apparatus and methods for providing fault tolerance of networks and network interface cards |
| DE10004432A1 (en) * | 2000-02-02 | 2001-08-09 | Siemens Ag | Network and network participants, in particular field device, for such a network |
| DE10047923C2 (en) * | 2000-09-27 | 2003-04-10 | Siemens Ag | Method for generating a connection redundancy for a serial communication system with a master unit and a plurality of slave units, which are connected to one another as a series of point-to-point connections in line topology, and a corresponding serial communication system |
-
2002
- 2002-02-22 DE DE10207529A patent/DE10207529B4/en not_active Expired - Fee Related
-
2003
- 2003-02-21 DE DE50301187T patent/DE50301187D1/en not_active Expired - Fee Related
- 2003-02-21 CA CA002477070A patent/CA2477070A1/en not_active Abandoned
- 2003-02-21 AT AT03709639T patent/ATE304761T1/en not_active IP Right Cessation
- 2003-02-21 WO PCT/DE2003/000555 patent/WO2003073704A1/en active IP Right Grant
- 2003-02-21 CN CNB038044242A patent/CN100574241C/en not_active Expired - Fee Related
- 2003-02-21 EP EP03709639A patent/EP1476988B1/en not_active Expired - Lifetime
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1722515A1 (en) * | 2005-05-11 | 2006-11-15 | Siemens Aktiengesellschaft | Ring system |
| WO2006120217A1 (en) * | 2005-05-11 | 2006-11-16 | Nokia Siemens Networks Gmbh & Co. Kg | Ring system |
| EP1727313A1 (en) * | 2005-05-25 | 2006-11-29 | Siemens Aktiengesellschaft | Ring network and method for automatic protection switching |
| WO2006125544A1 (en) * | 2005-05-25 | 2006-11-30 | Nokia Siemens Networks Gmbh & Co. Kg | Ring network and method for automatic protection switching |
| WO2008037781A1 (en) * | 2006-09-29 | 2008-04-03 | Nokia Siemens Networks Gmbh & Co. Kg | Method for protection switching in ring topologies |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2003073704A1 (en) | 2003-09-04 |
| DE50301187D1 (en) | 2005-10-20 |
| EP1476988B1 (en) | 2005-09-14 |
| DE10207529B4 (en) | 2004-07-29 |
| DE10207529A1 (en) | 2003-09-11 |
| CN100574241C (en) | 2009-12-23 |
| EP1476988A1 (en) | 2004-11-17 |
| CN1640066A (en) | 2005-07-13 |
| ATE304761T1 (en) | 2005-09-15 |
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