Addressing of redundant elements in a communication network

The invention relates to a system and a method for addressing of at least two mutually redundant subscribers in a communication network, wherein the subscribers is permanently assigned a unique physical address in the communication network.

From the <patcit id="pcit0001" dnum="US6392990B1"><text>US 6392990 B1</text></patcit> discloses a method for the treatment of defects in components of a network interface. The method is provided for running on a computer in a network having a plurality of computers, said computer mutually redundant with redundant lines have connected interface units. The method provides a transparent recovery from network failures sure by providing a list of addresses of the computers in the network. The computer periodically checks the communication links to one or more of the other computer until it receives a reply in the form of its network address of at least one computer. The computer then uses the network address of the other computer to monitor the communications link to this computer until possibly no longer responds to the other computer. In the event that it receives no response, the computer to the network address of the other computer of the redundant interface unit.

From the <patcit id="pcit0002" dnum="US5473599A"><text>US 5,473,599</text></patcit> is a system and a method is known by means of which data packets can be sent in a communication network via a virtual address of an active router from a group of routers. Here, the sender does not care about the actual physical address of the router.

From Li et al. (1998) RCF 2281 - CISCI Hot Standby Router Protocol (HSRP) is also known that multiple routers provide a single virtual router and the network nodes send their data to the virtual router.

The invention has for its object to increase the availability of communication links within a communication network.

This object is achieved by a system having the features recited in claim. 1

The object is also achieved by a method with the features mentioned in the claim. 4

To increase the communication availability communication buses are often designed with high availability. This is achieved by establishing a communication ring, or by doubling the communication lines, for. Example. In order not only to dominate the failure of the communication link but also the failure of a communication unit, in many cases, the communication unit is redundant realized, because the next vulnerability is the fault-tolerant communication. Functional units, z. B. redundant control units or peripheral units with redundant communication unit which are connected to a communication bus (line or ring) or to a redundant communication bus must be addressable. Here are two contradictory requirements: For all functions for which the redundancy should be hidden, the functional unit should be only one address. Such functions include, for. Example, the single-channel connection tailed process peripherals. This address should be switchable. For all functions for the redundancy to be disclosed, the functional unit or its communication unit should get as many addresses as redundant components in the redundant unit are present. So a user-friendly diagnosis is possible as such. As an error, the respective address of the vulnerable component may be clearly identified. there is the same requirement for the maintenance and for information functions. interested Again not the commonality of redundant components but exactly the status data of each component. The redundant communication unit may be constructed n-channel (n&gt; 1) in general. The present invention satisfies the two described seemingly contradictory requirements. As a participant in the communication network or as a node here are communication units and, where appropriate, referred to the partial units.

According to an advantageous embodiment of the invention the parent unit is provided for detecting a failure of communication links to the subscribers and for detecting a failure of the subscriber. The functionality of the communication is therefore monitored by the higher-level communication unit (or partner unit).

If the parent unit reveals the failure of the preferred channel, it can cause the currently selected as a reserve unit of the redundant communication unit to a switch or transfer the switched address. Advantageously, therefore, the parent unit is provided for selecting a preferred communication route from the communication routes to a group associated with participants. A group mutually redundant subscriber is referred to below as the redundancy group. Each of the redundant sub-units has two addresses. A first address is assigned permanently to the part unit. The other part is the second address, the switchable address called. The switchable address is activated when the priority channel and disabled in all belonging to this redundancy group redundant channels. If the preferred channel switchable address is set to active on the standby channel. About the switchable address the common functionality of the group is reached.

According to a further advantageous embodiment of the invention, the system for addressing of at least two mutually redundant subscribers in a communication network part of an industrial automation system. For all functions in which the allocation to the redundant channels or redundant communication units has no relevance, the component behaves like a single-channel component. These functions include such. B. Read process data / write and process alarms. For these functions, the redundant power component on both the communication ring and the redundant communication bus behaves as a single component. This has the advantage that the redundancy remains hidden. In automation technology, the aim is that a partner component that processes only process data or process alarms from redundant peripheral unit does not have to worry about redundancy. If the preferred channel subunit fails, repeat the associated communication system, z. B. Ethernet, automatically the communication request and since the switchable address responds to the other side, the communication is now on the former standby channel without the single-channel communication unit must be active themselves , Only those functional units which must address the individual subunits (z. B. for diagnostics and maintenance), must have knowledge of the redundancy by know the addresses of the subunits. This has the advantage that for repair and maintenance all the necessary information (such as data ortrichtige of the subunits) can be read and written by the same means as in the single-channel components. This has therefore, in their view also the advantage that the redundancy remains hidden.

To a simple automatic addressing - especially when booting the system - to achieve, activated according to a further advantageous embodiment of the invention, one of the redundant subscriber group an assigned third unique in the communication network physical address as the communication network valid each group assigned second address and disable the remaining redundant members of the group the second address.

The invention will be described and explained in more detail with reference to the embodiments shown in the figures.

Show it:<dl id="dl0001"><dt>1 shows</dt><dd>a system for addressing two mutually redundant subscribers in a communication network,</dd><dt>FIG 2</dt><dd>a system of mutually redundant subscribers in a communication network with a redundantly designed communication bus, </dd><dt>FIG 3</dt><dd>a communication unit with two redundant sub-units and</dd><dt>FIG 4</dt><dd>a system for addressing each redundant subscribers in a communications network illustrating the communication links within the system.</dd></dl>

<figref idrefs="f0001">figure 1</figref> shows a system for addressing two mutually redundant subscribers 3, 4 in a communication network 5. Participants 3, 4 are in the embodiment of Figure 1 mutually redundant communication units form a functional unit 11. The mutually redundant subscribers 3, 4 form a group 6. The redundant participants 3, 4 can communicate via a communication bus 10 in the communication network. 5 To the communication bus 10 is a higher-level unit 7 is connected, which has a communication unit 12 as well as a functional unit thirteenth For communication, various communication routes 8 available. The first redundant subscriber 3 is permanently assigned a unique in the communication network 5 physical address. 1 The second redundant subscriber 4 is another permanently assigned in the communication network 5 unique physical address. 9 The group 6 of the mutually redundant subscribers 3, 4 is another in the communication network 5 assigned unique physical address 2, which is on each of the two redundant subscribers 3, 4 of the Group 6 as in the communication network 5 valid address be activated and deactivated. This activation and deactivation takes place in the embodiment of<figref idrefs="f0001">figure 1</figref> at the initiative of the parent unit 7. In this case, the parent unit 7 exactly one of the two redundant subscribers 3, 4 further address 2 to date, ie the address 2 at the respective subscriber 3, 4. Among the other party 3, 4 however, this address 2 deactivated by the parent entity. 7 A thus made assigning physical addresses 1, 2, 9 causes the mutually redundant subscribers 3, 4 are uniquely addressable or accessible both via their respective first address 1, 9 individually, as a group 6 of the physical address 2 are addressable. The physical address 2 is thereby assigned to one of the two formed by the redundant subscribers 3, 4 and the respective bus segments communication channels as priority channel. The respective other communication channel is kept as a spare channel. The functionality of the communication is monitored by the parent unit. 7 If the parent unit 7 exposes the failure or trouble communicating with the primary channel, it causes the currently set as reserve participants 3 or 4 of the group to a switchover or takeover of the so-called switched address. 2

In previously known system is only one identical address for both units or only one address for the preferred channel and an address for the standby channel is provided in the mutually redundant units either. If the preferred channel then takes over the part of communication unit previously standby channel was, as soon as possible the priority channel and the address of the preferred channel. From the user perspective but all communication unit then changes the address. In both methods previously known, however it is not possible to request reasonable to solve that each of the redundant units in the network to be uniquely addressable. Diagnostic and maintenance tools therefore do not know when the prior art known methods by which the two mutually redundant communication units communicate.

<figref idrefs="f0001">figure 2</figref> shows another embodiment of a system for addressing two mutually redundant subscribers in a communications network having a redundant bus system. Communication units 22, 31, 33 are coupled to each other via redundant communication lines 20, 21, z. B. communication buses. The communication units 22, 31, 33 fulfill communication tasks of functional units 23, 32, 34. In the communication unit 33 of the functional unit 34 is a redundant communication unit, which 35 or 36 includes two redundant sub-units. Likewise, the communication unit 22 of the parent function unit 23 is configured as a redundant parent communication unit. Another participant of the communication is the single-channel function unit 32, which communicates via the single-channel communication unit 31st

The communication units 22, 31 and the sub-units 35, 36 is a fixed physical unique in the communication network address is assigned in each case. In the embodiment of<figref idrefs="f0001">figure 2</figref> this physical address is executed as a so-called MAC address 24, 25, 26 and 27 (MAC = Media Access Control). As a MAC address usually large by 48-bit hexadecimal numbers is shown and generally referred unchangeable identification number of a subscriber in a communications network. The MAC address is a hardware address that uniquely identifies a node on the network. According to the OSI reference model (OSI = Open System Interconnection), which is also referred to as 7-layer model, the second layer, called the data link layer, divided into two sub-layers, the MAC layer is the lower layer. The MAC layer serves to organize the bit transmission layer into logical groups of information that frame so-called, as well as for fault finding, for controlling the flow of data and to identify the computer in the network. It is now being introduced for the redundant sub-units 35, 36 an additional address 28th That is, each of the sub-units 35, 36 receive two addresses. The respective first address 26, 27 is fixed to the respective sub-unit associated with 35 and 36 respectively, while the other 28 address the so-called switchable address is. The switchable address 28 is activated when the priority channel and disables the spare channel. If the preferred channel or communication link 20 or 21 the second address 28 is set to active on the standby channel. About the second address 28 the common functionality of the functional unit 34 is reached.

One possible implementation on MAC address level is as follows: Each of the two sub-units 35, 36 includes two globally unique MAC addresses 26, 27 and 28. Those sub-unit 35, 36 which is ready for operation after first switching on the system first, activated independently both their addresses 26, 27 and 28 - an address permanently assigned address 26 or 27 and the address other than the so-called switched address 28 the one sub-unit 35, 36, which starts subsequently activated only her as a dedicated address 26 and 27. The so-called switched address 28 makes this sub-unit 35, 36 inactive. However, the sub-unit 35, 36 is preparing the connected MAC address 28 of the other sub-unit 35, to take 36, if other sub-unit 35, 36 fails.

The higher-level communication unit 22 is in the embodiment of <figref idrefs="f0001">figure 2</figref> redundant realized, that is, that they by means of the address 24 and via the communication path 21 is accessible via the communications link 20 by means of the address 25th The higher-level communication unit 22 has the task to monitor communications for redundant communication unit 33rd This monitoring involves both the primary channel (Primary) and the spare channel. In case of failure of the replacement channel (either by failure of the bus connection or failure of the respective reserve sub-unit 35 or 36) of this failure is reported to a master control system. If the preferred channel is sent by the higher-functional unit 23 to the respective reserve unit 35 and 36, a message even to be preferred channel. This sub-unit 35, 36 maintains its fixed address 26 or 27 and activates the switched address 28 for the preferred channel. The former primary channel commissioned both on the internal connection as well as the parent communication unit 22 to disable its preferred channel address 28 (if it has not already failed, and thus is communicatively no longer active).

The awarding of the switchable address is, for example, with one of the two methods described below: In the first proposed method, the higher-level communication unit managed 22, the switchable addresses and assigns them at every first activation of a redundant group. From the factory to each of the sub-units 35, 36, an address 26, 27 is set, the other address 28 is 0 or not active. Only at the start of the sub-unit 35, 36 in a redundant group, the second address 28 is used. The second proposed method, each sub-unit 35, 36 of the associated redundancy group communication unit 33 from the factory has set two globally unique addresses. For example, sub-unit 35 receives the address "a + x" and the sub-unit 36 ​​the address "b + y". When you turn the mutually redundant sub-units 35, 36 35 activates the first energized subunit its switchable address "x". The subsequently switched part unit 36 ​​rejects its switchable address "y" and adopts the address "x" as a switchable address.

Diagnostic and maintenance tools are mostly like the single-channel function unit 32 with a single-channel communication unit 31 realized. The single-channel communication unit 31 is in turn associated with a fixed physical address 29th The communication unit 31 communicates via a switch 30 to the redundant communication paths 20 and 21 diagnostic and maintenance tools know both addresses 26, 27 of the redundant communication unit 33, since the objective of diagnosis and maintenance, individual interchangeable sub-units 35, to diagnose 36 , When a communication request, a response independent of the respective hardware unit is required, which is possible with the proposed addressing mechanisms.

<figref idrefs="f0002">figure 3</figref> shows an embodiment of a functional unit 40 having a redundant communication unit which consists of two sub-units 41 and 42 respectively. The sub-units 41 and 42 communicate via communication links 43 and 44 with further not shown here subscribers in a communication network. The sub-units 41, 42 are addressable by physical addresses 46, 47, 48th Additionally, there is an internal communication link 45 between the two sub-units 41 and 42. Since the address described switching does not take place via the internal communications link 45, but via the external communication links 43, 44, the failure of the internal communication link may on one hand be controlled 45 and on the other hand addition of the failure the external communication links 43, 44 are identified and controlled.

<figref idrefs="f0002">figure 4</figref> serves to illustrate the communication relationships of a system for addressing within mutually redundant subscribers in a communication network. Shown is a functional unit 55 with a two-part units 56, 57 communication unit, a single-channel communication unit 53 with a single-channel communication unit 54 and a higher-level functional unit 51 with a master communication unit 52. The higher-level communication unit 52 is on the address 60 addressable and communicates via a Switch 58 with the redundant communication bus 50. the single-channel communication unit 54 is addressed via the address 61 and communicates via the switch 59 with the redundant communication bus 50. the sub-units 56, 57 of the redundant communication unit also communicate via the redundant communication bus 50 and are addresses 62 , 63 and 64, respectively addressable.

The arrows marked with the reference numeral 67 represent the majority of communication relationships are shown within the system. Over these communication relations z. B. Process data and process alarms to be replaced. This communication relations work regarding the redundant communication unit with the switched address 63 and are essentially equivalent to a communication session to a single-channel device. The arrows marked with the reference numeral 66 represent the communication relationships for maintenance and diagnostics to the sub-units 56, 57 of the communication unit. In addition, there are also not shown communication links with the functional unit 55. The communication links designated by the numeral 65 represent the functions which for communication monitoring and for the switchover when detecting a fault on the primary channel are required. Over these communication relationships and the communication failure is detected and reported to the spare channel. In the case illustrated the part unit 57 is the reserve unit and thus has its switchable address 63 is not activated.

In summary, the invention thus relates to a system and a method for addressing of at least two mutually redundant subscribers 3, 4 in a communication network 5, in which the users 3, 4 each have a first unique in the communication network 5 physical address 1, 9 permanently assigned is. In order to increase the availability of communication links within the communication network, it is proposed that a group 6 of mutually redundant subscribers 3, 4 each have a second associated unique physical address 2 in the communication network 5, wherein the group 6 associated second address 2 at the redundant subscribers 3, 4 of group 6 is in each case as in the communication network 5 valid address be activated and deactivated, at least one parent unit 7 one at a time to activate the second address 2 is exactly one of the redundant subscribers 3, 4 of group 6 and to deactivate 2 the second address is provided in the remaining redundant subscribers 3, 4 of the group. 6