Title of Invention	METHOD AND APPARATUS FOR MEDIUM-REDUNDANT OPERATION OF A TERMINAL IN A NETWORK
Abstract	The invention relates to a method and device for modern-redundant expression of a terminal in a network. The device comprises.;a first transmission device (6) of a physical bit transmission plane which is connected to a network component (9) via a first connection medium (8) disposed between the first transmission device(6) and a network component (9) and which can produce an error signal during automatic numbering of link to the network component (9) if no physical link or if a defective link to the network component(9) exists,another transmission device (7) on the physical transmission plane,which is connected to the network(4) via another connection medium (10); and a control device(5) which is connected to9 the first transmission device (6) and the other transmission device (7) in order to describtion the first transmission device(6) as a reaction to the errror signal tharefore the other connection medium (10) by means of the other transmission device(7).The invention also relates to a method for operating said device.

Title of Invention

METHOD AND APPARATUS FOR MEDIUM-REDUNDANT OPERATION OF A TERMINAL IN A NETWORK

Abstract

The invention relates to a method and device for modern-redundant expression of a terminal in a network. The device comprises.;a first transmission device (6) of a physical bit transmission plane which is connected to a network component (9) via a first connection medium (8) disposed between the first transmission device(6) and a network component (9) and which can produce an error signal during automatic numbering of link to the network component (9) if no physical link or if a defective link to the network component(9) exists,another transmission device (7) on the physical transmission plane,which is connected to the network(4) via another connection medium (10); and a control device(5) which is connected to9 the first transmission device (6) and the other transmission device (7) in order to describtion the first transmission device(6) as a reaction to the errror signal tharefore the other connection medium (10) by means of the other transmission device(7).The invention also relates to a method for operating said device.

Full Text	- 1 - Description Method and apparatus for medium-redundant operation of a terminal in a network The invention relates to a method and an apparatus for media- redundant operation of a terminal in a network. When electronic terminals are being linked, for example computers or electronically controlled manufacturing machines, by means of a network, it is desirable for media redundancy to be provided for each terminal. A terminal may in this case be any desired device which has a network component of. the network or is connected to such a component. The expression network component covers any apparatus which can send and/or receive data packets in the network. In this sense, network components may, for example, be switches or hubs. A switch is an active network component for connecting individual segments of a network to one another. A hub is likewise an active network component, for example a star coupler. The expression connecting medium is used for components of a network via which data and signals can be physically transmitted between different network components. These include, for example, twisted pair cables, coaxial cables and fiber-optical cables. The expression medium covers not only the pure connecting medium but also its connecting components to the network on the one hand (network components) and to the terminal on the other hand (transmission devices). However, since the connecting media in particular may be affected by possible failures, for example as a result of external destruction, these represent the major focus for the design of a media-redundant connection. If a terminal is connected to the network via two physically PCT/DE2003/004130 - 2 - 2002P11728WOUS independent media (media redundancy), then, if one of the media fails, safe and reliable communication is nevertheless possible with the terminal. Since disturbances to .individual media are unavoidable, manufacturing failures can be avoided by means of media redundancy in the case of media disturbances, for example in production operations. Media redundancy can be achieved in a terminal by, for example, equipping the appliance with two transmission devices each having their own media access controller, which controllers are connected to the network via different connecting media. This configuration can be provided in the terminal, for example in the form of two separate network boards. In this case, conventional network components may be used for the inclusion of a terminal. Furthermore, failure monitoring is possible even into the terminal itself, from application to application, in all network protocol layers separately for the two different network links. However, this has the disadvantage that two network boards are necessarily required in each terminal, and this leads to an increase in the costs of the terminals. Furthermore, in this situation, each terminal must be assigned two media access control addresses (MAC addresses) as well as two Internet Protocol addresses (IP addresses). Failure monitoring and a change between the two connections via the two network boards takes place at a higher network protocol layer, generally at the application layer, and is thus done using computer capacity in the terminal. Failure monitoring at the application layer thus results in the computer power of the terminal being restricted with regard to the actual application. The switching times in the event of a disturbance in one of the media are typically in the region of 100 ms. PCT/DE2003/004130 - 3 - 2002P11728WOUS Another implemented approach for achieving media redundancy is referred to as the ring redundancy approach. This approach is described, by way of example, in the document "Industrial Ethernet™ startet durch - Switching und l00Mbit/s in der industriellen Kommunikation" [Industrial Ethernet™ starts by - switching and 100 Mbit/s in industrial communication], K. Glas, 1998. In this case, one or more terminals is or are connected to a ring network. If this network is interrupted at one point, then all of the terminals and network components in the ring network are still connected to one another, such that they are still fully serviceable. In this solution, the terminals each require only one network board with one transmission device and one media access controller. In the event of a disturbance, switching takes place at a so-called second network protocol layer ("layer 2") . At the application layer, no program is required for failure monitoring, although no monitoring from application to application is possible, either. Another disadvantage is that the switching times are in the region of 200 ms. A further disadvantage is that it is not possible to use standard switch components to produce the network. The only switch components which may be used are those which are specially designed for use in a network with ring redundancy. One object of the invention is to create an improved method and an improved apparatus for safe, reliable, low-cost and fast media-redundant operation of a terminal in a network, on the basis of media redundancy achieved by duplication of the transmission devices and of the associated media access controllers. PCT/DE2003/004130 - 4 - 2002P11728WOUS According to the invention, the object is achieved by a method as claimed in claim 1, and by an apparatus as claimed in claim 10. In particular, the invention comprises the following ideas: a terminal is connected to a network via two transmission devices in a physical bit transmission layer, of which devices only one is ever active at one time, in order to interchange data with the network. The transmission devices are connected to a single control device. If the first (active) of the two transmission devices finds that there is no good connection between it and the network via a first connecting medium,.it is deactivated by the control device, the further transmission device is activated as the active transmission device, and an electronic failure message is sent into the network, so that the network can adapt itself to the change that has occurred with respect to the activity status of the two transmission devices, and its consequences with regard to the passing on of data for that terminal. The connection between the terminal and the network is then provided by means of the second (redundant) connection via the further transmission device and the further connecting medium. One advantage of the invention is that a method and an apparatus are provided which allow very fast switching of the redundant link between a terminal and a network. The expression "fast switching" describes the fact that the data interchange between the terminal and the network, which is handled via a first connecting medium, can be continued after a very short time, that is to say quickly, via the further connecting medium in the event of a disturbance or an interruption in this first connecting medium. Since the PCT/DE2003/004130 - 5 - 2002P11728WOUS change from the first connecting medium to the further connecting medium requires only the deactivation of the first transmission device, for which the disturbance was found, and the activation of the further transmission device in the physical bit transmission layer, as well as the sending of an electronic failure message, the change can be carried out in less than about 1 ms. The switching need not be initiated at a higher network protocol layer. The invention may not only be implemented in an electronic circuit, but may also be implemented by means of software, which interacts with an electronic circuit. An apparatus according to the invention can be produced at low cost and is suitable not only for use in appliances to be designed from new, but also for use with old appliances, in order to connect them to the network with media redundancy. One development of the invention comprises a data packet to be transmitted from the terminal to the network being analyzed by an analysis device, a media access control address being determined in the process and being assigned to a media access controller for the terminal, and the media access control address being inserted into the electronic failure message during the production of the electronic failure message. These method steps make it possible to carry out the method independently of any prior knowledge of the media access control address of the media access controller for the terminal. One advantageous embodiment of the method according to the invention furthermore provides for the network to analyze the failure message and to adapt itself to it in such a way that data packets which are addressed to the terminal are passed on PCT/DE2003/004130 - 6 - 2002P11728WOUS to the further connecting medium. This means that the network can adapt itself in a very short time to the change in the connecting medium via which the terminal is connected to the network. This avoids unnecessary network traffic, and data packets are no longer passed to the connecting medium which is faulty or is subject to a disturbance. Another embodiment of the method according to the invention provides that the network component analyzes the failure message and adapts its address addressing table for the media access controller for the terminal in such a way that data packets which are addressed to the terminal are passed on to the further connecting medium. This allows particularly fast switching of the network, since only the settings of the network component need be changed. Furthermore, one advantageous embodiment of the method according to the invention comprises the use of a network component, to which the first and the further connecting medium are connected. In this case, the network component just has to internally redirect the data packets that are addressed to that terminal to another connection in order to switch the connection to that terminal from the first (disturbed) connecting medium to the further connecting medium. This can be done particularly easily and quickly when using a network component that is designed appropriately for this purpose. However, one particularly advantageous refinement for the method according to the invention is regarded as the use of a further network component, to which the further connecting medium is connected. This also achieves redundancy PCT/DE2003/004130 - 7 - 2002P11728WOUS with regard to a failure of one of the network components to which the terminal is connected directly. A further development of the method consists in that a communication is carried out from the terminal with the network component by means of a standard network protocol, in particular an Internet Control Message Protocol (ICMP), in order to check the serviceability of the network component. This allows the terminal additionally to react even to those failures of the network component in which a sound physical connection still exists between the transmission device and the network component, despite the failure. It is also advantageously possible to provide for an application to be run on the terminal, and for the application to interchange checking data packets after predetermined time intervals with another network component which is connected to that network component, in order to determine whether the network component is serviceable. This means that it is possible to monitor the failure of the network component when the latter is not able to communicate by means of the standard network protocol. Another expedient embodiment of the method provides for the other network component to produce an application failure signal if it has not received any of the checking data packets after a predetermined number of predetermined time intervals. This makes it possible to detect a failure of the application on the other network component. If, for example, the application in the terminal is instructed to interchange data with the other application in the other network component, PCT/DE2003/004130 - 8 - 2002P11728WOUS then it is important to be able to distinguish between "network disturbances" and application failures,, in the event of communication disturbances. With regard to the apparatus according to the invention, one advantageous embodiment provides that the first and the further connecting medium are connected to the network component. This makes it possible to switch particularly quickly to the second connecting medium in the event of a failure of the first connecting medium, since the network component just has to switch internally to another connection. However, an appropriately designed network component must be used for an embodiment such as this. One alternative advantageous development of the apparatus according to the invention provides that the further transmission device is connected to another network component via the further connecting medium. This means that the apparatus is also provided with redundancy with regard to a failure of the network component or of the other network component. Another advantageous embodiment of the apparatus provides that the transmission device, the further transmission device and the control device are arranged on a network board in the terminal. This allows the apparatus to be integrated in a terminal in a simple manner. This also makes it possible to connect commercially available personal computers with media redundancy to a network. One expedient development consists in that the transmission device, the further transmission device and the control device are arranged in a redundancy switch, PCT/DE2003/004130 - 9 - 2002P11728WOUS which is connected to the terminal. A redundancy switch such as this allows terminals which are not designed for this purpose to be connected with media redundancy, without having to modify the terminals. A further expedient development of the apparatus provides for the redundancy switch to have an additional transmission device in the physical bit transmission layer, in order to interchange data packets with the terminal. This development allows a network-compatible terminal to be connected to the network with media redundancy, without any additional precautions. In addition, this development can be used to connect a terminal not only via two separate connecting media, but also via two different connecting media types, for example via a twisted pair cable and via a fiber-optical cable. A further advantageous embodiment of the apparatus provides an analysis device for analysis of a data packet to be transmitted into the network from the terminal, in order to determine a media access control address and in order to insert the media access control address into the electronic failure message. This embodiment can be operated without any prior knowledge of the media access control address of the terminal, and is particularly advantageous when the media access control address changes as a result of replacement of the media access controller in the course of servicing or upgrading work on the terminal, since the new media access control address is determined automatically in this embodiment. PCT/DE2003/004130 2002P11728WOUS - 10 - One expedient development of the invention is for the control device to have the analysis device. This results in a compact embodiment. Another advantageous development of the invention provides for the control device to be an electronically programmable logic device (ELPD). A control device such as this costs little and can easily be matched to a media access control address for the terminal. This development means that it is possible to change particularly quickly from the connecting medium to the other connecting medium. Another development of the apparatus provides for the control device to comprise the media access controller. This development makes it possible to design a very compact and low- cost embodiment of the invention. The invention will be explained in more detail in the following text using exemplary embodiments and with reference to a drawing, in which: Figure 1 shows a terminal which is connected with media redundancy to a network; Figure 2 shows a schematic illustration of a network; Figure 3 shows another embodiment of a terminal, which is connected with media redundancy to a network; Figure 4 shows an apparatus for media-redundant operation of a terminal in a network; and PCT/DE2003/004130 - 11 - 2002P11728WOUS Figure 5 shows a further apparatus for media-redundant operation of a terminal in a network. Figure 1 shows a terminal 1 which is connected with media redundancy to a network 4. By way of example, it is assumed here that the network 4 is an Ethernet network. However, the invention can also be used in other network types. The terminal 1 has a processor (CPU) 2, which controls the terminal 1 and runs applications on the terminal 1. The processor 2 is connected to a control device 5 which, in this embodiment, comprises a media access controller (MAC) 3. The media access controller 3 controls the connection of the terminal 1 to the network 4 on a so-called second network protocol layer ("layer 2") . The media access controller 3 is assigned a unique media access control address (MAC address), by means of which the media access controller 3 for the terminal 1 is distinguished from other media access controllers for further terminals in the network 4. The control device 5 is connected to a transmission device 6 for a so-called physical bit transmission layer ("physical layer device"-PHY) and to a further transmission device 7 in the physical bit transmission layer. The transmission device 6 and the further transmission device 7 convert the data transmitted to them from the media access controller 3 into physical signals, which can be transmitted via a first connecting medium 8 and via a further connecting medium 10. The connecting media may comprise coaxial cables, twisted-pair cables, glass-fiber cables, wireless connections, etc. The transmission device 6, the further transmission device 7 and the media access controller 3 may expediently be combined on one network board 17. PCT/DE2003/004130 - 12 - 2002P11728WOUS The transmission device 6 is connected to a network component 9 via the first connecting medium 8. The further transmission device 7 can likewise be connected to the network component 9 via the further connecting medium 10. In a situation such as this, media redundancy exists for the connection of the terminal to the network only with regard to the connecting media 8 and 10. In this situation, an appropriate network component 9 must be used, which internally converts the connection to the terminal to the other connecting medium in the event of a failure of one of the connecting media. However, the following text will consider the situation as illustrated in Figure 1, in which the further transmission device 7 is connected to another network component 11 via the further connecting medium 10. The network component 9 and the other network component 11 may each in particular be a switch, a HUB or the like. The network component 9 and the further network component 11 are connected to one another via another connecting medium 12. During operation, only the first transmission device 6 or the further transmission device 7 is in each case active. The first transmission device 6 and the further transmission device 7 are activated/deactivated by the control device 5 in this embodiment. The first transmission device 6 and the further transmission device 7 carry out autonomous automatic monitoring, in order to determine whether there is a sound physical connection via the appropriate first connecting medium 8 and the further connecting medium 10, respectively, to the network component 9 and to the other network component 11. This check is referred to as a PCT/DE2003/004130 - 13 - 2002P11728WOUS connection status check or a link status check. During this check, the MAC address that is assigned to the media access controller 3 is not transmitted to the first network component 9 and to the other network component 11. Those skilled in the art will be familiar with the method of operation of the link status check by the first transmission device 6 and the further transmission device 7 in the physical bit transmission layer. By way of example, the link status check will be explained for the first connecting medium 8. It is assumed that the first connecting medium 8 comprises an optical fiber and a further optical fiber, as is normal for optical connecting media. The first transmission device 6 uses the optical fiber to send test signals based on a protocol for the bit transmission layer to the network component 9. During normal operation, the network component 9 "reflects" the test signals to the further optical fiber. If it is now also assumed that the first connecting medium 8 is detached from the network component 9, then the latter identifies from the lack of the "reflected" test signals that the first connecting medium 8 has been disturbed. A so-called "far end fault" is present. In order to ensure that either only the first transmission device 6 or only the further transmission device 7 is active at one time, and sends data packets using the MAC address assigned to the media access controller 3, it is possible for the network 4 to configure itself such that all of the data packets directed to the terminal 1 from the network 4 are transmitted to the active transmission device of the physical bit transmission layer. PCT/DE2003/004130 - 14 - 2002P11728WOUS In order to explain the reaction to a media failure, it is assumed that the first transmission device 6 is active initially. If a disturbance now occurs on the first connecting medium 8, then the first transmission device 6 finds during the link status check that there is no longer a sound physical link to the network component 9. The failure of the connection is transmitted to the control device 5, as is indicated by an arrow 13. Furthermore, the fault can also be transmitted to other components of the terminal, for example the processor and to programs in higher network protocol layers, in particular the application layer, as is indicated by arrow 14. As soon as the connecting media failure is found by the first transmission device 6, it is deactivated by the control device 5 and the further transmission device 7 is activated, as is indicated by other arrows 15a and 15b. In order to allow the network 4 to continue to transmit the data packets intended for the terminal 1 via the further connecting medium 10 to the terminal 1 a.failure message is first of all sent via the other network component 11 to the network. The failure message is advantageously in the form of a so-called multicast message. This message therefore contains no addressee and is passed on to all of the network components in the network 4 which belong to the network in the physical bit transmission layer. The network can also be formed by a network element which comprises all of those network components to which data packets of the terminal 1 can be passed on exclusively on an MAC address basis. PCT/DE2003/004130 - 15 - 2002P11728WOUS Intelligent network components in the network, in particular switches and other terminals, can adapt their MAC address addressing tables on the basis of the failure message, which includes the MAC address assigned to the media access controller 3. The expression intelligent network component in this case covers any network component which can analyze the data packets received by it and is able to react in some way to a result of the analysis. The analysis of the failure message and the adaptation of the addressing tables can be carried out by any intelligent network components or, by way of example, predominantly by the network component 9. After a failure of the connection to the terminal 1 via the first connecting medium 8 and the first transmission device, this network component 9 can pass on all of the data packets intended for the terminal 1 via the other connecting medium 12 to the other network component 11. In the situation where the two transmission devices 6 and 7 are connected via the connecting media 8 and 10 only to the one network component 9, the data packets which are intended for the terminal 1 must be passed on internally in the network component 9 to a connection which is connected to the further connecting medium 10. The deactivation and the switching from the first transmission device 6 to the further transmission device 7 can be carried out in the second network protocol layer (layer 2) or in a higher network protocol layer. The switching can also be carried out by a control device 5, which need not comprise the media access controller 3. The failure message can likewise be produced in the second network PCT/DE2003/004130 - 16 - 2002P11728WOUS protocol layer (layer 2), for example by means of an electronically programmable logic device ("Electronic Programmable Logic Device" (EPLD)) or an application-specific integrated circuit (ASIC), or can be produced in a higher network protocol layer. The failure message can be coded in such a Way that the media failure and switching operations are indicated to all the communication partners. The production of the failure message may also include data being read in from a memory, in particular from a read only memory (ROM). In addition to the monitoring of a failure of one of the connecting media 8, 10, it is also possible to monitor for a fault in the network component 9 and in the other network component 11. If the network component 9 and the other network component 11 are each in the form of an intelligent component, then failure identification can be ensured by means of cyclic sending of requests to the network component 9 and to the other network component 11 on the basis of a standard protocol, such as the ICMP (Internet Control Message Protocol). The correctly operating network component 9 and the other network component 11 respond to the requests. Figure 2 shows an enlarged detail from the network 4. The same features in Figures 1 and 2 are provided with the same reference symbols. In the exemplary embodiment shown in Figure 2, an additional network component 23 or further terminals 25, 2 6, which are likewise connected directly to the network component 9 and to the other network component 11, respectively, can be checked in the manner described above. PCT/DE2003/004130 - 17 - 2002P11728WOUS The check for failure identification via an ICMP communication can selectively also be triggered or initiated by an application in the terminal 1 using the so-called watchdog method (monitoring method). In this case, a communication based on the standard protocol, in particular an ICMP communication, with the additional network component 23 or with one of the further terminals 25, 2 6 which are connected directly to the network component 9 to which the transmission device 6 (which is assumed to be active in this case) is connected, is carried out at specific time intervals. The additional network component 23 or one of the further terminals 25, 26 can use the lack of this communication in accordance with the standard protocol to deduce that the network component 9 has failed. The application in the terminal 1 can likewise produce an "other component failure signal" if no more request data packets are received by the application in the terminal 1 in accordance with the standard protocol, when such request data packets are initiated by the other application in the additional network component 23 or by one of the further terminals 25, 26. In the embodiment shown in Figure 1, the first transmission device 6 and the further transmission device 7 were connected to the network component 9 and to the further network component 11. Figure 2 shows an embodiment of an additional terminal 24, in which the transmission device 28 and the further transmission device 29 are connected to the additional network component 23 via two different connecting media, a connecting medium 40 and a further connecting medium 41. This embodiment also ensures connecting media redundancy for the additional terminal 24. In this embodiment, however, the PCT/DE2003/004130 - 18 - 2002P11728WOUS redundancy is lost in the event of a total failure of the additional network component 23. In the embodiment shown in Figure 1, the network component 9 was connected directly to the other network component 11 via the other connecting medium 12. Figure 2 shows a different network topology. The additional network component 23 is arranged between the network component 9 and the other network component 11, and subdivides the other connecting medium 12 into two parts 12a, 12b. Further additional network components can also be arranged between the network component 9 and the other network component 11, provided that the configuration ensures that multicast data packets from the further additional network components are passed on from the network component 9 to the further network component 11, and vice-versa. If the further terminals 25, 26 are intended to be connected to the network with media redundancy, in addition to the terminal 1, then it is worthwhile providing a first connecting medium 43 to the network component 9, and a second connecting medium 4 4 to the other network component 11, from each of the further terminals 25, 26. This creates a clear network topology, and additionally means that all of the terminals are also redundantly connected to the network in the event of a failure of the network component 9 or of the other network component 11. Figure 3 shows another embodiment of the invention. Identical features in Figures 1 to 3 are provided with identical reference symbols. In this embodiment, a control device 5 is arranged between the first transmission device 6 PCT/DE2003/004130 - 19 - 2002P11728WOUS and the further transmission device 7 on the one hand, and the media access controller 3 on the other hand. The control device 5 may be an electronically programmable logic device (EPLD) or an application-specific integrated circuit (ASIC). In this embodiment, the failure signals from the first transmission device 6 and the further transmission device 7 are transmitted to the control device 5. In the event of a connecting media failure, the control device 5 carries out the "switching". This may be done transparently for higher network layers. This allows very fast switching. The switching time is in the region of about 1 ms or less. In addition, in this embodiment as well, the connecting media failure can also be transmitted to the higher network protocol layers. Figure 4 shows a further embodiment of the invention. Identical features in Figures 1 to 4 are provided with identical reference symbols. In this embodiment, a redundancy switch 20 comprises the first transmission device 6, the further transmission device 7 and the control device 5. The redundancy switch 2 0 is separated from the terminal 1 and is connected to it via a connecting line 21. A data packet to be sent from the terminal 1 to the network 4 comprises the MAC address which is associated with the media access controller 3 for the terminal 1. An analysis device 22 for the redundancy switch 20, which is connected to the control device 5, determines the MAC address which is required for production of the failure message, on the basis of the data packet to be sent. The control device 5 operates in the manner that has been described above for the embodiment shown in Figure 1. The redundancy switch 20 allows PCT/DE2003/004130 - 20 - 2002P11728WOUS terminals which are not designed in a redundant form to be easily connected with media redundancy to the network 4. Figure 5 shows a further embodiment of the invention, similar to that illustrated in Figure 4. Identical features in Figures 4 and 5 are provided with identical reference symbols. In addition to the embodiment shown in Figure 4, the redundancy switch shown in Figure 5 has an additional transmission device 31 in the physical bit transmission layer, which is connected to the control device 5. The additional transmission device 31 is connected via an additional connecting medium 33 to another transmission device 32 in the physical bit transmission layer. The other transmission device 32 is formed by the network board 17. The embodiment shown in Figure 5 is distinguished in that the redundancy switch 20 is designed such that it can be used with the terminal 1, which is not designed in a redundant form, in order to connect the terminal 1 with media redundancy to the network 4. Furthermore, the control device 5 in this embodiment comprises the analysis device 22, as is indicated by a dashed line. PCT/DE2003/004130 - 21 - 2002P11728WOUS Patent Claims 1. A method for media-redundant operation of a terminal (1) in a network (4), in which the following steps are carried out: - automatic monitoring of a connection, which is formed via a first connecting medium (8) between a first transmission device (6) in the terminal (1) and a network component (9) , by means of the first transmission device (6); - production of a failure signal by the first transmission device (6) if no physical connection or a faulty physical connection is found via the first connecting medium (8) to the network component (9) during automatic monitoring of the connection; and - carrying out the following steps as a reaction to the failure signal: - deactivation of the first transmission device (6) by means of a control device (5) which is connected to the first transmission device (6) and to a further transmission device (7) of the terminal; - activation of the further transmission device (7) by means of the control device (5) , with a sound physical connection being reproduced between the terminal (1) and the network (4) via a further connecting medium (10) ; and - sending of an electronic failure message by means of the further transmission device (7) via the further connecting medium (10) to the network (4) for registration of the further transmission device. PCT/DE2003/004130 - 22 - 2002P11728WOUS 2. The method as claimed in claim 1, characterized in that a data packet to be transmitted from the terminal (1) to the network (4) is analyzed by an analysis device (22) , a media access control address is determined in the process and is assigned to a media access controller (3) for the terminal (1), and the media access control address is inserted into the electronic failure message during the production of the electronic failure message. 3. The method as claimed in claim 1 or 2, characterized in that the network (4) analyzes the failure message and matches itself to it in such a way that data packets which are addressed to the terminal (1) are passed on to the further connecting medium (10). 4. The method as claimed in claim 1 or 2, characterized in that the network component (9) analyzes the failure message and adapts its address addressing table for the media access controller (3) for the terminal (1) in such a way that data packets which are addressed to the terminal (1) are passed on to the further connecting medium (10). 5. The method as claimed in one of the preceding claims, characterized in that a network component is used, to which the first and the further connecting medium (8, 10) are connected. PCT/DE2003/004130 - 23 - 2002P11728WOUS 6. The method as claimed in one of claims 1 to 4, characterized in that another network component (11) is used, to which the further connecting medium (10) is connected. 7. The method as claimed in one of the abovementioned claims, characterized in that a communication is carried out from the terminal (1) with the network component (9) by means of a standard network protocol, in particular an Internet Control Message Protocol (ICMP), in order to check the serviceability of the network component (9). 8. The method as claimed in one of the abovementioned claims, characterized in that an application is run on the terminal (1), and the application interchanges checking data packets after predetermined time intervals with another network component (23) which is connected to the network component (9) , in order to determine whether the network component (9) is serviceable. 9. The method as claimed in claim 8, characterized in that the other network component (23) produces an application failure signal if it has not received any of the checking data packets after a predetermined number of predetermined time intervals. 10. An apparatus for media-redundant operation of a terminal (1) in a network (4) having - a transmission device (6) in a physical bit transmission layer, with the first transmission PCT/DE2003/004130 - 24 - 2002P11728WOUS device (6) being connected to the network component (9) via a connecting medium (8) which is arranged between the first transmission device (6) and a network component (9) , and, during automatic monitoring of a connection to the network component (9) via the connecting medium (8), producing a failure signal if there is no physical connection or a faulty physical connection to the network component (9); - a further transmission device (7) in the physical bit transmission layer, with the further transmission device (7) being connected to the ' network (4) via a further connecting medium (10); and - a control device (5) which is connected to the first transmission device (6) and to the further transmission device (7) and, as a reaction to the failure signal, deactivates the first transmission device {6), activates the further transmission device (7), and sends an electronic failure message via the further connecting medium (10) by means of the further transmission device (7) into the network (4). 11. The apparatus as claimed in claim 10, characterized in that the first and the further connecting medium (8, 10) are connected to the network component (9) . 12. The apparatus as claimed in claim 10, characterized in that the further transmission device (7) is connected to another network component (11) via the further connecting medium (10) . PCT/DE2003/004130 - 25 - 2002P11728WOUS 13. The apparatus as claimed in one of claims 10 to 12, characterized in that the transmission device , (6) , the further transmission device (7) and the control device (3) are arranged on a network board (17) in the terminal (1). 14. The apparatus as claimed in one of claims 10 to 12, characterized in that the transmission device (6) , the further transmission device (7) and the control device (5) are arranged in a redundancy switch (20), which is connected to the terminal (1). 15. The apparatus as claimed in claim 14, characterized in that the redundancy switch (20). has an additional transmission device (31) in the physical bit transmission layer, in order to interchange data packets with the terminal (1). 16. The apparatus as claimed in one of claims 10 to 15, characterized by an analysis device (22) for analysis of a data packet to be transmitted into the network (4) from the terminal (1), in order to determine a media access control address and in order to insert the media access control address into the electronic failure message. 17. The apparatus as claimed in claim 16, ' characterized in that the control device (5) comprises the analysis device (22). PCT/DE2003/004130 - 26 - 2002P11728WOUS 18. The apparatus as claimed in one of claims 10 to 17, characterized in that the control device (5) is an electronically programmable logic device (ELPD). 19. The apparatus as claimed in one of claims 10 to 13, characterized in that the control device (5) comprises a media access controller (3) . The invention relates to a method and device for modern-redundant expression of a terminal in a network. The device comprises.;a first transmission device (6) of a physical bit transmission plane which is connected to a network component (9) via a first connection medium (8) disposed between the first transmission device(6) and a network component (9) and which can produce an error signal during automatic numbering of link to the network component (9) if no physical link or if a defective link to the network component(9) exists,another transmission device (7) on the physical transmission plane,which is connected to the network(4) via another connection medium (10); and a control device(5) which is connected to9 the first transmission device (6) and the other transmission device (7) in order to describtion the first transmission device(6) as a reaction to the errror signal tharefore the other connection medium (10) by means of the other transmission device(7).The invention also relates to a method for operating said device.

Full Text

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Description
Method and apparatus for medium-redundant operation of a
terminal in a network
The invention relates to a method and an apparatus for media-
redundant operation of a terminal in a network. When electronic
terminals are being linked, for example computers or
electronically controlled manufacturing machines, by means of a
network, it is desirable for media redundancy to be provided
for each terminal. A terminal may in this case be any desired
device which has a network component of. the network or is
connected to such a component. The expression network component
covers any apparatus which can send and/or receive data packets
in the network. In this sense, network components may, for
example, be switches or hubs. A switch is an active network
component for connecting individual segments of a network to
one another. A hub is likewise an active network component, for
example a star coupler. The expression connecting medium is
used for components of a network via which data and signals can
be physically transmitted between different network components.
These include, for example, twisted pair cables, coaxial cables
and fiber-optical cables. The expression medium covers not only
the pure connecting medium but also its connecting components
to the network on the one hand (network components) and to the
terminal on the other hand (transmission devices). However,
since the connecting media in particular may be affected by
possible failures, for example as a result of external
destruction, these represent the major focus for the design of
a media-redundant connection. If a terminal is connected to the
network via two physically

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independent media (media redundancy), then, if one of the media
fails, safe and reliable communication is nevertheless possible
with the terminal. Since disturbances to .individual media are
unavoidable, manufacturing failures can be avoided by means of
media redundancy in the case of media disturbances, for example
in production operations.
Media redundancy can be achieved in a terminal by, for example,
equipping the appliance with two transmission devices each
having their own media access controller, which controllers are
connected to the network via different connecting media. This
configuration can be provided in the terminal, for example in
the form of two separate network boards. In this case,
conventional network components may be used for the inclusion
of a terminal. Furthermore, failure monitoring is possible even
into the terminal itself, from application to application, in
all network protocol layers separately for the two different
network links. However, this has the disadvantage that two
network boards are necessarily required in each terminal, and
this leads to an increase in the costs of the terminals.
Furthermore, in this situation, each terminal must be assigned
two media access control addresses (MAC addresses) as well as
two Internet Protocol addresses (IP addresses). Failure
monitoring and a change between the two connections via the two
network boards takes place at a higher network protocol layer,
generally at the application layer, and is thus done using
computer capacity in the terminal. Failure monitoring at the
application layer thus results in the computer power of the
terminal being restricted with regard to the actual
application. The switching times in the event of a disturbance
in one of the media are typically in the region of 100 ms.

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Another implemented approach for achieving media redundancy is
referred to as the ring redundancy approach. This approach is
described, by way of example, in the document "Industrial
Ethernet™ startet durch - Switching und l00Mbit/s in der
industriellen Kommunikation" [Industrial Ethernet™ starts by -
switching and 100 Mbit/s in industrial communication], K. Glas,
1998. In this case, one or more terminals is or are connected
to a ring network. If this network is interrupted at one point,
then all of the terminals and network components in the ring
network are still connected to one another, such that they are
still fully serviceable. In this solution, the terminals each
require only one network board with one transmission device and
one media access controller. In the event of a disturbance,
switching takes place at a so-called second network protocol
layer ("layer 2") . At the application layer, no program is
required for failure monitoring, although no monitoring from
application to application is possible, either. Another
disadvantage is that the switching times are in the region of
200 ms. A further disadvantage is that it is not possible to
use standard switch components to produce the network. The only
switch components which may be used are those which are
specially designed for use in a network with ring redundancy.
One object of the invention is to create an improved method and
an improved apparatus for safe, reliable, low-cost and fast
media-redundant operation of a terminal in a network, on the
basis of media redundancy achieved by duplication of the
transmission devices and of the associated media access
controllers.

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According to the invention, the object is achieved by a method
as claimed in claim 1, and by an apparatus as claimed in
claim 10.
In particular, the invention comprises the following ideas: a
terminal is connected to a network via two transmission devices
in a physical bit transmission layer, of which devices only one
is ever active at one time, in order to interchange data with
the network. The transmission devices are connected to a single
control device. If the first (active) of the two transmission
devices finds that there is no good connection between it and
the network via a first connecting medium,.it is deactivated by
the control device, the further transmission device is
activated as the active transmission device, and an electronic
failure message is sent into the network, so that the network
can adapt itself to the change that has occurred with respect
to the activity status of the two transmission devices, and its
consequences with regard to the passing on of data for that
terminal. The connection between the terminal and the network
is then provided by means of the second (redundant) connection
via the further transmission device and the further connecting
medium.
One advantage of the invention is that a method and an
apparatus are provided which allow very fast switching of the
redundant link between a terminal and a network. The expression
"fast switching" describes the fact that the data interchange
between the terminal and the network, which is handled via a
first connecting medium, can be continued after a very short
time, that is to say quickly, via the further connecting medium
in the event of a disturbance or an interruption in this first
connecting medium. Since the

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change from the first connecting medium to the further
connecting medium requires only the deactivation of the first
transmission device, for which the disturbance was found, and
the activation of the further transmission device in the
physical bit transmission layer, as well as the sending of an
electronic failure message, the change can be carried out in
less than about 1 ms. The switching need not be initiated at a
higher network protocol layer. The invention may not only be
implemented in an electronic circuit, but may also be
implemented by means of software, which interacts with an
electronic circuit. An apparatus according to the invention can
be produced at low cost and is suitable not only for use in
appliances to be designed from new, but also for use with old
appliances, in order to connect them to the network with media
redundancy.
One development of the invention comprises a data packet to be
transmitted from the terminal to the network being analyzed by
an analysis device, a media access control address being
determined in the process and being assigned to a media access
controller for the terminal, and the media access control
address being inserted into the electronic failure message
during the production of the electronic failure message. These
method steps make it possible to carry out the method
independently of any prior knowledge of the media access
control address of the media access controller for the
terminal.
One advantageous embodiment of the method according to the
invention furthermore provides for the network to analyze the
failure message and to adapt itself to it in such a way that
data packets which are addressed to the terminal are passed on

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to the further connecting medium. This means that the network
can adapt itself in a very short time to the change in the
connecting medium via which the terminal is connected to the
network. This avoids unnecessary network traffic, and data
packets are no longer passed to the connecting medium which is
faulty or is subject to a disturbance.
Another embodiment of the method according to the invention
provides that the network component analyzes the failure
message and adapts its address addressing table for the media
access controller for the terminal in such a way that data
packets which are addressed to the terminal are passed on to
the further connecting medium. This allows particularly fast
switching of the network, since only the settings of the
network component need be changed.
Furthermore, one advantageous embodiment of the method
according to the invention comprises the use of a network
component, to which the first and the further connecting medium
are connected. In this case, the network component just has to
internally redirect the data packets that are addressed to that
terminal to another connection in order to switch the
connection to that terminal from the first (disturbed)
connecting medium to the further connecting medium. This can be
done particularly easily and quickly when using a network
component that is designed appropriately for this purpose.
However, one particularly advantageous refinement for the
method according to the invention is regarded as the use of a
further network component, to which the further connecting
medium is connected. This also achieves redundancy

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with regard to a failure of one of the network components to
which the terminal is connected directly.
A further development of the method consists in that a
communication is carried out from the terminal with the network
component by means of a standard network protocol, in
particular an Internet Control Message Protocol (ICMP), in
order to check the serviceability of the network component.
This allows the terminal additionally to react even to those
failures of the network component in which a sound physical
connection still exists between the transmission device and the
network component, despite the failure.
It is also advantageously possible to provide for an
application to be run on the terminal, and for the application
to interchange checking data packets after predetermined time
intervals with another network component which is connected to
that network component, in order to determine whether the
network component is serviceable. This means that it is
possible to monitor the failure of the network component when
the latter is not able to communicate by means of the standard
network protocol.
Another expedient embodiment of the method provides for the
other network component to produce an application failure
signal if it has not received any of the checking data packets
after a predetermined number of predetermined time intervals.
This makes it possible to detect a failure of the application
on the other network component. If, for example, the
application in the terminal is instructed to interchange data
with the other application in the other network component,

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then it is important to be able to distinguish between "network
disturbances" and application failures,, in the event of
communication disturbances.
With regard to the apparatus according to the invention, one
advantageous embodiment provides that the first and the further
connecting medium are connected to the network component. This
makes it possible to switch particularly quickly to the second
connecting medium in the event of a failure of the first
connecting medium, since the network component just has to
switch internally to another connection. However, an
appropriately designed network component must be used for an
embodiment such as this.
One alternative advantageous development of the apparatus
according to the invention provides that the further
transmission device is connected to another network component
via the further connecting medium. This means that the
apparatus is also provided with redundancy with regard to a
failure of the network component or of the other network
component.
Another advantageous embodiment of the apparatus provides that
the transmission device, the further transmission device and
the control device are arranged on a network board in the
terminal. This allows the apparatus to be integrated in a
terminal in a simple manner. This also makes it possible to
connect commercially available personal computers with media
redundancy to a network.
One expedient development consists in that the transmission
device, the further transmission device and the control device
are arranged in a redundancy switch,

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which is connected to the terminal. A redundancy switch such as
this allows terminals which are not designed for this purpose
to be connected with media redundancy, without having to modify
the terminals.
A further expedient development of the apparatus provides for
the redundancy switch to have an additional transmission device
in the physical bit transmission layer, in order to interchange
data packets with the terminal. This development allows a
network-compatible terminal to be connected to the network with
media redundancy, without any additional precautions. In
addition, this development can be used to connect a terminal
not only via two separate connecting media, but also via two
different connecting media types, for example via a twisted
pair cable and via a fiber-optical cable.
A further advantageous embodiment of the apparatus provides an
analysis device for analysis of a data packet to be transmitted
into the network from the terminal, in order to determine a
media access control address and in order to insert the media
access control address into the electronic failure message.
This embodiment can be operated without any prior knowledge of
the media access control address of the terminal, and is
particularly advantageous when the media access control address
changes as a result of replacement of the media access
controller in the course of servicing or upgrading work on the
terminal, since the new media access control address is
determined automatically in this embodiment.

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One expedient development of the invention is for the control
device to have the analysis device. This results in a compact
embodiment.
Another advantageous development of the invention provides for
the control device to be an electronically programmable logic
device (ELPD). A control device such as this costs little and
can easily be matched to a media access control address for the
terminal. This development means that it is possible to change
particularly quickly from the connecting medium to the other
connecting medium.
Another development of the apparatus provides for the control
device to comprise the media access controller. This
development makes it possible to design a very compact and low-
cost embodiment of the invention.
The invention will be explained in more detail in the following
text using exemplary embodiments and with reference to a
drawing, in which:
Figure 1 shows a terminal which is connected with media
redundancy to a network;
Figure 2 shows a schematic illustration of a network;
Figure 3 shows another embodiment of a terminal, which is
connected with media redundancy to a network;
Figure 4 shows an apparatus for media-redundant operation of a
terminal in a network; and

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Figure 5 shows a further apparatus for media-redundant
operation of a terminal in a network.
Figure 1 shows a terminal 1 which is connected with media
redundancy to a network 4. By way of example, it is assumed
here that the network 4 is an Ethernet network. However, the
invention can also be used in other network types. The terminal
1 has a processor (CPU) 2, which controls the terminal 1 and
runs applications on the terminal 1. The processor 2 is
connected to a control device 5 which, in this embodiment,
comprises a media access controller (MAC) 3. The media access
controller 3 controls the connection of the terminal 1 to the
network 4 on a so-called second network protocol layer ("layer
2") . The media access controller 3 is assigned a unique media
access control address (MAC address), by means of which the
media access controller 3 for the terminal 1 is distinguished
from other media access controllers for further terminals in
the network 4. The control device 5 is connected to a
transmission device 6 for a so-called physical bit transmission
layer ("physical layer device"-PHY) and to a further
transmission device 7 in the physical bit transmission layer.
The transmission device 6 and the further transmission device 7
convert the data transmitted to them from the media access
controller 3 into physical signals, which can be transmitted
via a first connecting medium 8 and via a further connecting
medium 10. The connecting media may comprise coaxial cables,
twisted-pair cables, glass-fiber cables, wireless connections,
etc. The transmission device 6, the further transmission device
7 and the media access controller 3 may expediently be combined
on one network board 17.

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The transmission device 6 is connected to a network component 9
via the first connecting medium 8. The further transmission
device 7 can likewise be connected to the network component 9
via the further connecting medium 10. In a situation such as
this, media redundancy exists for the connection of the
terminal to the network only with regard to the connecting
media 8 and 10. In this situation, an appropriate network
component 9 must be used, which internally converts the
connection to the terminal to the other connecting medium in
the event of a failure of one of the connecting media.
However, the following text will consider the situation as
illustrated in Figure 1, in which the further transmission
device 7 is connected to another network component 11 via the
further connecting medium 10. The network component 9 and the
other network component 11 may each in particular be a switch,
a HUB or the like. The network component 9 and the further
network component 11 are connected to one another via another
connecting medium 12.
During operation, only the first transmission device 6 or the
further transmission device 7 is in each case active. The first
transmission device 6 and the further transmission device 7 are
activated/deactivated by the control device 5 in this
embodiment. The first transmission device 6 and the further
transmission device 7 carry out autonomous automatic
monitoring, in order to determine whether there is a sound
physical connection via the appropriate first connecting medium
8 and the further connecting medium 10, respectively, to the
network component 9 and to the other network component 11. This
check is referred to as a

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connection status check or a link status check. During this
check, the MAC address that is assigned to the media access
controller 3 is not transmitted to the first network component
9 and to the other network component 11.
Those skilled in the art will be familiar with the method of
operation of the link status check by the first transmission
device 6 and the further transmission device 7 in the physical
bit transmission layer. By way of example, the link status
check will be explained for the first connecting medium 8. It
is assumed that the first connecting medium 8 comprises an
optical fiber and a further optical fiber, as is normal for
optical connecting media. The first transmission device 6 uses
the optical fiber to send test signals based on a protocol for
the bit transmission layer to the network component 9. During
normal operation, the network component 9 "reflects" the test
signals to the further optical fiber. If it is now also assumed
that the first connecting medium 8 is detached from the network
component 9, then the latter identifies from the lack of the
"reflected" test signals that the first connecting medium 8 has
been disturbed. A so-called "far end fault" is present.
In order to ensure that either only the first transmission
device 6 or only the further transmission device 7 is active at
one time, and sends data packets using the MAC address assigned
to the media access controller 3, it is possible for the
network 4 to configure itself such that all of the data packets
directed to the terminal 1 from the network 4 are transmitted
to the active transmission device of the physical bit
transmission layer.

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In order to explain the reaction to a media failure, it is
assumed that the first transmission device 6 is active
initially. If a disturbance now occurs on the first connecting
medium 8, then the first transmission device 6 finds during the
link status check that there is no longer a sound physical link
to the network component 9. The failure of the connection is
transmitted to the control device 5, as is indicated by an
arrow 13. Furthermore, the fault can also be transmitted to
other components of the terminal, for example the processor and
to programs in higher network protocol layers, in particular
the application layer, as is indicated by arrow 14.
As soon as the connecting media failure is found by the first
transmission device 6, it is deactivated by the control device
5 and the further transmission device 7 is activated, as is
indicated by other arrows 15a and 15b. In order to allow the
network 4 to continue to transmit the data packets intended for
the terminal 1 via the further connecting medium 10 to the
terminal 1 a.failure message is first of all sent via the other
network component 11 to the network. The failure message is
advantageously in the form of a so-called multicast message.
This message therefore contains no addressee and is passed on
to all of the network components in the network 4 which belong
to the network in the physical bit transmission layer. The
network can also be formed by a network element which comprises
all of those network components to which data packets of the
terminal 1 can be passed on exclusively on an MAC address
basis.

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Intelligent network components in the network, in particular
switches and other terminals, can adapt their MAC address
addressing tables on the basis of the failure message, which
includes the MAC address assigned to the media access
controller 3. The expression intelligent network component in
this case covers any network component which can analyze the
data packets received by it and is able to react in some way to
a result of the analysis.
The analysis of the failure message and the adaptation of the
addressing tables can be carried out by any intelligent network
components or, by way of example, predominantly by the network
component 9. After a failure of the connection to the terminal
1 via the first connecting medium 8 and the first transmission
device, this network component 9 can pass on all of the data
packets intended for the terminal 1 via the other connecting
medium 12 to the other network component 11.
In the situation where the two transmission devices 6 and 7 are
connected via the connecting media 8 and 10 only to the one
network component 9, the data packets which are intended for
the terminal 1 must be passed on internally in the network
component 9 to a connection which is connected to the further
connecting medium 10.
The deactivation and the switching from the first transmission
device 6 to the further transmission device 7 can be carried
out in the second network protocol layer (layer 2) or in a
higher network protocol layer. The switching can also be
carried out by a control device 5, which need not comprise the
media access controller 3. The failure message can likewise be
produced in the second network

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protocol layer (layer 2), for example by means of an
electronically programmable logic device ("Electronic
Programmable Logic Device" (EPLD)) or an application-specific
integrated circuit (ASIC), or can be produced in a higher
network protocol layer. The failure message can be coded in
such a Way that the media failure and switching operations are
indicated to all the communication partners. The production of
the failure message may also include data being read in from a
memory, in particular from a read only memory (ROM).
In addition to the monitoring of a failure of one of the
connecting media 8, 10, it is also possible to monitor for a
fault in the network component 9 and in the other network
component 11. If the network component 9 and the other network
component 11 are each in the form of an intelligent component,
then failure identification can be ensured by means of cyclic
sending of requests to the network component 9 and to the other
network component 11 on the basis of a standard protocol, such
as the ICMP (Internet Control Message Protocol). The correctly
operating network component 9 and the other network component
11 respond to the requests.
Figure 2 shows an enlarged detail from the network 4. The same
features in Figures 1 and 2 are provided with the same
reference symbols. In the exemplary embodiment shown in Figure
2, an additional network component 23 or further terminals 25,
2 6, which are likewise connected directly to the network
component 9 and to the other network component 11,
respectively, can be checked in the manner described above.

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The check for failure identification via an ICMP communication
can selectively also be triggered or initiated by an
application in the terminal 1 using the so-called watchdog
method (monitoring method). In this case, a communication based
on the standard protocol, in particular an ICMP communication,
with the additional network component 23 or with one of the
further terminals 25, 2 6 which are connected directly to the
network component 9 to which the transmission device 6 (which
is assumed to be active in this case) is connected, is carried
out at specific time intervals. The additional network
component 23 or one of the further terminals 25, 26 can use the
lack of this communication in accordance with the standard
protocol to deduce that the network component 9 has failed.
The application in the terminal 1 can likewise produce an
"other component failure signal" if no more request data
packets are received by the application in the terminal 1 in
accordance with the standard protocol, when such request data
packets are initiated by the other application in the
additional network component 23 or by one of the further
terminals 25, 26.
In the embodiment shown in Figure 1, the first transmission
device 6 and the further transmission device 7 were connected
to the network component 9 and to the further network component
11. Figure 2 shows an embodiment of an additional terminal 24,
in which the transmission device 28 and the further
transmission device 29 are connected to the additional network
component 23 via two different connecting media, a connecting
medium 40 and a further connecting medium 41. This embodiment
also ensures connecting media redundancy for the additional
terminal 24. In this embodiment, however, the

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redundancy is lost in the event of a total failure of the
additional network component 23.
In the embodiment shown in Figure 1, the network component 9
was connected directly to the other network component 11 via
the other connecting medium 12. Figure 2 shows a different
network topology. The additional network component 23 is
arranged between the network component 9 and the other network
component 11, and subdivides the other connecting medium 12
into two parts 12a, 12b. Further additional network components
can also be arranged between the network component 9 and the
other network component 11, provided that the configuration
ensures that multicast data packets from the further additional
network components are passed on from the network component 9
to the further network component 11, and vice-versa.
If the further terminals 25, 26 are intended to be connected to
the network with media redundancy, in addition to the terminal
1, then it is worthwhile providing a first connecting medium 43
to the network component 9, and a second connecting medium 4 4
to the other network component 11, from each of the further
terminals 25, 26. This creates a clear network topology, and
additionally means that all of the terminals are also
redundantly connected to the network in the event of a failure
of the network component 9 or of the other network component
11.
Figure 3 shows another embodiment of the invention. Identical
features in Figures 1 to 3 are provided with identical
reference symbols. In this embodiment, a control device 5 is
arranged between the first transmission device 6

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and the further transmission device 7 on the one hand, and the
media access controller 3 on the other hand. The control device
5 may be an electronically programmable logic device (EPLD) or
an application-specific integrated circuit (ASIC). In this
embodiment, the failure signals from the first transmission
device 6 and the further transmission device 7 are transmitted
to the control device 5. In the event of a connecting media
failure, the control device 5 carries out the "switching". This
may be done transparently for higher network layers. This
allows very fast switching. The switching time is in the region
of about 1 ms or less. In addition, in this embodiment as well,
the connecting media failure can also be transmitted to the
higher network protocol layers.
Figure 4 shows a further embodiment of the invention. Identical
features in Figures 1 to 4 are provided with identical
reference symbols. In this embodiment, a redundancy switch 20
comprises the first transmission device 6, the further
transmission device 7 and the control device 5. The redundancy
switch 2 0 is separated from the terminal 1 and is connected to
it via a connecting line 21. A data packet to be sent from the
terminal 1 to the network 4 comprises the MAC address which is
associated with the media access controller 3 for the terminal
1. An analysis device 22 for the redundancy switch 20, which is
connected to the control device 5, determines the MAC address
which is required for production of the failure message, on the
basis of the data packet to be sent. The control device 5
operates in the manner that has been described above for the
embodiment shown in Figure 1. The redundancy switch 20 allows

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terminals which are not designed in a redundant form to be
easily connected with media redundancy to the network 4.
Figure 5 shows a further embodiment of the invention, similar
to that illustrated in Figure 4. Identical features in Figures
4 and 5 are provided with identical reference symbols. In
addition to the embodiment shown in Figure 4, the redundancy
switch shown in Figure 5 has an additional transmission device
31 in the physical bit transmission layer, which is connected
to the control device 5. The additional transmission device 31
is connected via an additional connecting medium 33 to another
transmission device 32 in the physical bit transmission layer.
The other transmission device 32 is formed by the network board
17. The embodiment shown in Figure 5 is distinguished in that
the redundancy switch 20 is designed such that it can be used
with the terminal 1, which is not designed in a redundant form,
in order to connect the terminal 1 with media redundancy to the
network 4. Furthermore, the control device 5 in this embodiment
comprises the analysis device 22, as is indicated by a dashed
line.

PCT/DE2003/004130 - 21 -
2002P11728WOUS
Patent Claims
1. A method for media-redundant operation of a terminal (1)
in a network (4), in which the following steps are carried
out:
- automatic monitoring of a connection, which is formed
via a first connecting medium (8) between a first
transmission device (6) in the terminal (1) and a
network component (9) , by means of the first
transmission device (6);
- production of a failure signal by the first transmission
device (6) if no physical connection or a faulty
physical connection is found via the first connecting
medium (8) to the network component (9) during automatic
monitoring of the connection; and
- carrying out the following steps as a reaction to the
failure signal:
- deactivation of the first transmission device (6) by
means of a control device (5) which is connected to the
first transmission device (6) and to a further
transmission device (7) of the terminal;
- activation of the further transmission device (7) by
means of the control device (5) , with a sound physical
connection being reproduced between the terminal (1) and
the network (4) via a further connecting medium (10) ;
and
- sending of an electronic failure message by means of the
further transmission device (7) via the further
connecting medium (10) to the network (4) for
registration of the further transmission device.

PCT/DE2003/004130 - 22 -
2002P11728WOUS
2. The method as claimed in claim 1,
characterized
in that a data packet to be transmitted from the terminal
(1) to the network (4) is analyzed by an analysis device
(22) , a media access control address is determined in the
process and is assigned to a media access controller (3)
for the terminal (1), and the media access control address
is inserted into the electronic failure message during the
production of the electronic failure message.
3. The method as claimed in claim 1 or 2,
characterized
in that the network (4) analyzes the failure message and
matches itself to it in such a way that data packets which
are addressed to the terminal (1) are passed on to the
further connecting medium (10).
4. The method as claimed in claim 1 or 2,
characterized
in that the network component (9) analyzes the failure
message and adapts its address addressing table for the
media access controller (3) for the terminal (1) in such a
way that data packets which are addressed to the terminal
(1) are passed on to the further connecting medium (10).
5. The method as claimed in one of the preceding claims,
characterized
in that a network component is used, to which the first
and the further connecting medium (8, 10) are connected.

PCT/DE2003/004130 - 23 -
2002P11728WOUS
6. The method as claimed in one of claims 1 to 4,
characterized
in that another network component (11) is used, to which
the further connecting medium (10) is connected.
7. The method as claimed in one of the abovementioned claims,
characterized
in that a communication is carried out from the terminal
(1) with the network component (9) by means of a standard
network protocol, in particular an Internet Control
Message Protocol (ICMP), in order to check the
serviceability of the network component (9).
8. The method as claimed in one of the abovementioned claims,
characterized
in that an application is run on the terminal (1), and the
application interchanges checking data packets after
predetermined time intervals with another network
component (23) which is connected to the network component
(9) , in order to determine whether the network component
(9) is serviceable.
9. The method as claimed in claim 8,
characterized
in that the other network component (23) produces an
application failure signal if it has not received any of
the checking data packets after a predetermined number of
predetermined time intervals.
10. An apparatus for media-redundant operation of a terminal
(1) in a network (4) having
- a transmission device (6) in a physical bit transmission
layer, with the first transmission

PCT/DE2003/004130 - 24 -
2002P11728WOUS
device (6) being connected to the network component (9)
via a connecting medium (8) which is arranged between
the first transmission device (6) and a network
component (9) , and, during automatic monitoring of a
connection to the network component (9) via the
connecting medium (8), producing a failure signal if
there is no physical connection or a faulty physical
connection to the network component (9);
- a further transmission device (7) in the physical bit
transmission layer, with the further transmission device
(7) being connected to the ' network (4) via a further
connecting medium (10); and
- a control device (5) which is connected to the first
transmission device (6) and to the further transmission
device (7) and, as a reaction to the failure signal,
deactivates the first transmission device {6), activates
the further transmission device (7), and sends an
electronic failure message via the further connecting
medium (10) by means of the further transmission device
(7) into the network (4).
11. The apparatus as claimed in claim 10,
characterized
in that the first and the further connecting medium (8,
10) are connected to the network component (9) .
12. The apparatus as claimed in claim 10,
characterized
in that the further transmission device (7) is connected
to another network component (11) via the further
connecting medium (10) .

PCT/DE2003/004130 - 25 -
2002P11728WOUS
13. The apparatus as claimed in one of claims 10 to 12,
characterized
in that the transmission device , (6) , the further
transmission device (7) and the control device (3) are
arranged on a network board (17) in the terminal (1).
14. The apparatus as claimed in one of claims 10 to 12,
characterized
in that the transmission device (6) , the further
transmission device (7) and the control device (5) are
arranged in a redundancy switch (20), which is connected
to the terminal (1).
15. The apparatus as claimed in claim 14,
characterized
in that the redundancy switch (20). has an additional
transmission device (31) in the physical bit transmission
layer, in order to interchange data packets with the
terminal (1).
16. The apparatus as claimed in one of claims 10 to 15,
characterized by
an analysis device (22) for analysis of a data packet to
be transmitted into the network (4) from the terminal (1),
in order to determine a media access control address and
in order to insert the media access control address into
the electronic failure message.
17. The apparatus as claimed in claim 16, '
characterized
in that the control device (5) comprises the analysis
device (22).

PCT/DE2003/004130 - 26 -
2002P11728WOUS
18. The apparatus as claimed in one of claims 10 to 17,
characterized
in that the control device (5) is an electronically
programmable logic device (ELPD).
19. The apparatus as claimed in one of claims 10 to 13,
characterized
in that the control device (5) comprises a media access
controller (3) .

The invention relates to a method and device for modern-redundant expression of a terminal in a network. The device comprises.;a first transmission device (6) of a physical bit transmission plane which is connected to a network component (9) via a first connection medium (8) disposed between the first transmission device(6) and a network component (9) and which can produce an error signal during automatic numbering of link to the network component (9) if no physical link or if a defective link to the network component(9) exists,another transmission device (7) on the physical transmission plane,which is connected to the network(4) via another connection medium (10); and a control device(5) which is connected to9 the first transmission device (6) and the other transmission device (7) in order to describtion the first transmission device(6) as a reaction to the errror signal tharefore the other connection medium (10) by means of the other transmission device(7).The invention also relates to a method for operating said device.

Documents:

01520-kolnp-2005-abstract.pdf

01520-kolnp-2005-claims.pdf

01520-kolnp-2005-description complete.pdf

01520-kolnp-2005-drawings.pdf

01520-kolnp-2005-form 1.pdf

01520-kolnp-2005-form 2.pdf

01520-kolnp-2005-form 3.pdf

01520-kolnp-2005-form 5.pdf

01520-kolnp-2005-international publication.pdf

1520-KOLNP-2005-CORRESPONDENCE 1.1.pdf

1520-KOLNP-2005-FORM-27.pdf

1520-kolnp-2005-granted-abstract.pdf

1520-kolnp-2005-granted-claims.pdf

1520-kolnp-2005-granted-correspondence.pdf

1520-kolnp-2005-granted-description (complete).pdf

1520-kolnp-2005-granted-drawings.pdf

1520-kolnp-2005-granted-examination report.pdf

1520-kolnp-2005-granted-form 1.pdf

1520-kolnp-2005-granted-form 18.pdf

1520-kolnp-2005-granted-form 2.pdf

1520-kolnp-2005-granted-form 3.pdf

1520-kolnp-2005-granted-form 5.pdf

1520-kolnp-2005-granted-gpa.pdf

1520-kolnp-2005-granted-reply to examination report.pdf

1520-kolnp-2005-granted-specification.pdf

1520-KOLNP-2005-PA.pdf

abstract-01520-kolnp-2005.jpg

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Patent Number

235673

Indian Patent Application Number

1520/KOLNP/2005

PG Journal Number

31/2009

Publication Date

31-Jul-2009

Grant Date

29-Jul-2009

Date of Filing

02-Aug-2005

Name of Patentee

SIEMENS AKTIENGESELLSCHAFT

Applicant Address

WITTELSBACHERPLATZ 2, 80333 MUNICH

Inventors:

#	Inventor's Name	Inventor's Address
1	HOGA, CLEMENS	PANIERSPLATZ 13, 9040390403 NUREMBERG
2	NEITE, RUDOLF	FRANKENSTRASSE 10B, 91301 FORCHHEIM

PCT International Classification Number

H 04 L 12/00

PCT International Application Number

PCT/DE2003/004130

PCT International Filing date

2003-12-10

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10305415.4	2003-02-06	Germany