Patent Publication Number: US-2022236712-A1

Title: Automation network and method for transmitting data in an automation network

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The application is a continuation of International Patent Application PCT/EP2020/082075, filed 13 Nov. 2020, entitled AUTOMATION NETWORK AND METHOD FOR TRANSMITTING DATA IN AN AUTOMATION NETWORK, which claims the priority of German patent application DE 10 2019 131 823.8, filed 25 Nov. 2019, entitled AUTOMATISIERUNGSNETZWERK UND VERFAHREN ZUR DATENÜBERTRAGUNG IN EINEM AUTOMATISIERUNGSNETZWERK, each of which is incorporated by reference herein, in the entirety and for all purposes. 
    
    
     FIELD 
     The present invention relates to an automation network. Furthermore, the invention relates to a method for transmitting data in the automation network. 
     BACKGROUND 
     Automation networks are frequently operated as “field-bus systems”. These are industrial bus systems that allow for real-time capable control of the machines or systems of the automation network, wherein the machines or systems of the automation network are controlled via programmable logic controllers (PLCs). The PLC uses the field-bus system to communicate the field devices, e.g. sensors and actuators of the machines or systems of the automation network with the PLC. If a plurality of network subscribers send telegrams via the same data line in the automation network, which may be embodied as a wired or wireless bus system, there must be a way for the network subscribers to share the same data line for transmitting data. For this purpose, defined hierarchies and standardized protocols are provided. 
     In most cases, the field-bus systems operate in so-called “master-slave mode”. This means that at least one network subscriber is embodied as a master subscriber and takes over the control of the processes, while the other network subscribers, which may comprise a plurality of slave subscribers, take over the processing of partial tasks in the control mode of the automation network. The exchange of data in the automation network is carried out using telegrams that are output by the master subscriber to the slave subscribers. The slave subscribers read the output data addressed to them from the telegram and place their input data into the telegram and return the telegram to the master subscriber. 
     The automation networks are frequently embodied as Ethernet-based networks or as an Ethernet-based field bus. This means that the real-time capable protocol on which the telegram traffic in the automation network is based may e.g. be the EtherCAT protocol. An automation network with an underlying EtherCAT protocol, hereinafter referred to as EtherCAT network for short, which is known from the prior art, comprises a direct connection between the master subscriber and the individual network subscribers or slave subscribers. The master subscriber and the network subscribers or slave subscribers are therefore each connected to one another via a point-to-point connection without intermediate stations, e.g. in the form of network distributors, via a data line network. A telegram from the master subscriber passes through all the slave subscribers connected to the data line network one after the other, each of which processes the telegram on the fly, and the last slave subscriber returns the telegram to the master subscriber via the data line network. 
     In error mode, i.e. in the event that an interference has occurred on the line, e.g. due to a physical interruption of the transmission medium, the master subscriber may in this way only address the part of the slave subscribers via the data line network that is located upstream of the location of interference. 
     EP 1869836 B1 describes a method in which the last slave subscriber is reconnected to the master subscriber via a redundant data line network. The master subscriber sends a first telegram to the first slave subscriber, which passes through the remaining slave subscribers one after the other, and a second telegram to the last slave subscriber, which passes through the remaining slave subscribers one after the other in the opposite direction. In particular, the method ensures that the master subscriber may address both the slave subscribers upstream of the location of interference and the slave subscribers downstream of the location of interference, as viewed from the master subscriber, using telegrams during error mode. 
     If the EtherCAT network with the redundant data line network is extended by network distributors, which may be embodied as so-called switches or branches, the above-mentioned method can only be applied to a limited extent to those areas of the EtherCAT network in which only slave subscribers are arranged. A communication of the master subscriber via telegrams with all slave subscribers may thus not be operated further in error mode. 
     SUMMARY 
     The present invention provides an optimized automation network and an improved method for transmitting data in the proposed automation network. 
     EXAMPLES 
     According to a first aspect, an automation network is proposed. The automation network comprises a plurality of network subscribers comprising at least a master subscriber, at least a switch, and at least a slave subscriber. The master subscriber comprises master ports, the switch comprises switching ports, and the slave subscriber comprises slave ports, each comprising a transmitter for transmitting telegrams and a receiver for receiving telegrams. 
     The transmitter of a first master port is connected to the receiver of a first switching port via a first master communication path, and the transmitter of a second switching port is connected to the receiver of a second master port via the first master communication path. The transmitter of the second master port is connected to the receiver of the second switching port via a second master communication path, and the transmitter of the first switching port is connected to the receiver of the first master port via the second master communication path to form a first dual ring structure. 
     The transmitter of a third switching port is connected to the receiver of a first slave port via a first slave communication path, and the transmitter of a second slave port is connected to the receiver of a fourth switching port via the first slave communication path. The transmitter of the fourth switching port is connected to the receiver of the second slave port via a second slave communication path, and the transmitter of the first slave port is connected to the receiver of the third switching port via the second slave communication path to form a second dual ring structure. 
     The master subscriber is embodied to send two telegrams based on the same data packet. The master subscriber is embodied to output a first telegram to the switch via the transmitter of the first master port and via the first master communication path, and to output a second telegram to the switch via the transmitter of the second master port and via the second master communication path. The switch is embodied to receive the first telegram via the receiver of the first switching port, and to forward the first telegram to the receiver of the first slave port via the transmitter of the third switching port and via the first slave communication path. The slave subscriber is embodied to forward the first telegram, after processing in passing, to the receiver of the fourth switching port via the transmitter of the second slave port via the first slave communication path. 
     The switch is embodied to forward the first telegram received via the receiver of the fourth switching port to the receiver of the second master port via the transmitter of the second switching port via the first master communication path. The switch is embodied to receive the second telegram via the receiver of the second switching port and to forward it via the transmitter of the fourth switching port to the receiver of the second slave port via the second slave communication path. The slave subscriber is embodied to forward the second telegram via the transmitter of the first slave port over the second slave communication path to the receiver of the third switching port. The switch is embodied to forward the second telegram received via the receiver of the third switching port to the receiver of the first master port via the transmitter of the first switching port via the second master communication path. The switch and the slave subscriber are in error mode configured to return the first telegram to the master subscriber so that the master subscriber receives the first telegram via the receiver of the first master port and/or to return the second telegram to the master subscriber so that the master subscriber receives the second telegram via the receiver of the second master port. 
     According to a second aspect, a method for transmitting data in the automation network is proposed. The automation network comprises a plurality of network subscribers comprising at least a master subscriber, at least a switch, and at least a slave subscriber. The master subscriber comprises master ports, the switch comprises switching ports, and the slave subscriber comprises slave ports, each of which comprises a transmitter for transmitting telegrams and a receiver for receiving telegrams. 
     The transmitter of a first master port is connected to the receiver of a first switching port via a first master communication path and the transmitter of a second switching port is connected to the receiver of a second master port via the first master communication path. The transmitter of the second master port is connected to the receiver of the second switching port via a second master communication path, and the transmitter of the first switching port is connected to the receiver of the first master port via the second master communication path to embody a first dual ring structure. 
     The transmitter of a third switching port is connected to the receiver of a first slave port via a first slave communication path and the transmitter of a second slave port is connected to the receiver of a fourth switching port via the first slave communication path. The transmitter of the fourth switching port is connected to the receiver of the second slave port via a second slave communication path and the transmitter of the first slave port is connected to the receiver of the third switching port via the second slave communication path to embody a second dual ring structure. 
     The master subscriber sends two telegrams based on the same data packet, wherein a first telegram is output to the switch via the transmitter of the first master port and via the first master communication path, and a second telegram is output to the switch via the transmitter of the second master port and via the second master communication path. The switch receives the first telegram via the receiver of the first switching port and forwards it to the receiver of the first slave port via the transmitter of the third switching port and via the first slave communication path. After processing on the fly, the slave subscriber forwards the first telegram via the transmitter of the second slave port via the first slave communication path to the receiver of the fourth switching port. 
     The switch forwards the first telegram received via the receiver of the fourth switching port to the receiver of the second master port via the transmitter of the second switching port via the first master communication path. The switch receives the second telegram via the receiver of the second switching port and forwards it to the receiver of the second slave port via the transmitter of the fourth switching port via the second slave communication path. The slave subscriber forwards the second telegram to the receiver of the third switching port via the transmitter of the first slave port via the second slave communication path. The switch forwards the second telegram received via the receiver of the third switching port to the receiver of the first master port via the transmitter of the first switching port via the second master communication path. The switch and the slave subscriber are embodied to return the first telegram to the master subscriber in error mode so that the master subscriber receives the first telegram via the receiver of the first master port and/or to return the second telegram to the master subscriber in error mode so that the master subscriber receives the second telegram via the receiver of the second master port. 
     According to a third aspect, a method for transmitting data in an automation network for an error mode is proposed. The automation network comprises at least one master subscriber, at least one switch, and at least one slave subscriber. The master subscriber comprises master ports, the switch comprises switching ports, and the slave subscriber comprises slave ports, each comprising a transmitter and a receiver. The master subscriber is configured to output a first telegram to a first switching port via a first master port and a first master communication path, and to output a second telegram to a second switching port via a second master port and a second master communication path. 
     The switch is configured to forward the first telegram to a first slave port of a slave subscriber via a first slave communication path, and to forward the second telegram to a second slave port of a slave subscriber via a second slave communication path. In error mode, the switch and the slave subscriber are configured to return the first telegram to the master subscriber such that it receives the first telegram via the first master port and/or to return the second telegram to the master subscriber such that it receives the second telegram via the second master port. 
     In spite of the error mode, which may include a line interference in the first dual ring structure, i.e. e.g. a physical interruption of the transmission medium on the first master communication path and/or an interruption on the second master communication path, and/or a line interference of the second dual ring structure, i.e. a physical interruption of the transmission medium on the first slave communication path and/or a physical interruption of the transmission medium on the second slave communication path, safe operation of the automation network may be maintained. Consequently, the proposed automation network with the redundant dual ring topology provides improved resilience and guarantees a real-time capability of the automation network. Advantageously, the proposed automation network is thereby not limited to a master-slave structure, but may be extended by a switch that may comprise one and/or more network distributors, i.e., switches or branches, and continues to guarantee communication between the master subscriber with the slave subscriber despite the error mode, so that the master subscriber may reach any network subscriber provided that the network subscriber is still connected to the master subscriber via a communication path. 
     In particular, the proposed method may reduce the telegram traffic in the automation network compared to other redundancy methods, i.e., the overhead in the automation network may be cut in half, since in other redundancy methods the corresponding telegram is basically doubled at a branch, i.e., a switch, regardless of whether a line interference occurs in the automation network or not. 
     In a further embodiment, a plurality of slave subscribers is provided that are arranged in a chain. The slave subscribers in the chain are each connected via the first slave port and via the second slave port. The chain of slave subscribers is connected to the third switching port and to the fourth switching port via the first slave communication path and the second slave communication path. A chain of slave subscribers may be connected to the second dual ring structure and connected to the third switching port and the fourth switching port. Advantageously, the behavior of a slave subscriber in the chain in error mode does not differ from the behavior in normal mode, i.e., without line interference. This is because a slave subscriber in the chain processes a telegram via an integrated processor on the fly, and only on the forward path of the telegram, which may be formed by the first slave communication path, for example, while the last slave subscriber sends the telegram back to the master subscriber via the second slave communication path, for example, due to a short-circuited second slave port. 
     In the event of a line interference between two adjacent slave subscribers in the chain, the slave subscriber adjacent to the interference, where the adjacent slave subscriber e.g. be located adjacent to the interrupted data line, i.e. to the corresponding fault, detects that there is no connection to a subsequent slave subscriber, so that the adjacent slave subscriber short-circuits the transmitter of the second slave port to the receiver of the second slave port in order to return the telegram via the second slave communication path. The second slave communication path is e.g. connected to the receiver of the second slave port. 
     In another embodiment, a plurality of switches is provided that is arranged in a chain. The chain of switches is connected to the first master port and the second master port via the first master communication path and via the second master communication path. The first telegram and/or the second telegram each have address information indicating to the corresponding switch whether the first telegram is intended for the first slave communication path and/or whether the second telegram is intended for the second slave communication path and/or whether the first telegram is intended for the first master communication path and/or whether the second telegram is intended for the second master communication path. 
     The proposed automation network may advantageously comprise a plurality of switches, to each of which a chain of slave subscribers may be connected in a double ring structure. The proposed automation network may guarantee simple expandability of the network, while at the same time continuing to maintain the fail-safety of the automation network. In addition, the proposed automation network together with the method offers the advantage that adaptation to individual system requirements is possible. The address information in the telegram means that the respective telegram may quickly be forwarded in the automation network to the network subscriber intended for the telegram. 
     In another embodiment, the switch comprises a first network distributor and a second network distributor, each having a plurality of distribution ports. A first distribution port of the first network distributor corresponds to the first switching port of the switch, and a second distribution port of the first network distributor corresponds to the third switching port of the switch. The first network distributor is connected to a first distribution port of the second network distributor via a third distribution port of the first network distributor. 
     The switch may comprise a first and a second network distributor, wherein the first network distributor and the second network distributor may be embodied to output telegrams via the distribution ports and, based on the address information of the telegrams, to the network subscribers for which the telegrams are intended. The network distributors may be embodied as switches or as branches, so that their function may be used advantageously. In particular, this may improve the compatibility of the network subscribers in the automation network. 
     In a further embodiment, a network distributor adjacent to an interference and/or a switch adjacent to an interference is configured in error mode to set a first error information for the first telegram and/or a second error information for the second telegram and to return the first telegram with the first error information to the master subscriber via the second master communication path and/or the second telegram with the second error information back to the master subscriber via the first master communication path. 
     The switch adjacent to the interference, i.e. the switch which detects the interference, which may particularly be a line interference, on the first master communication path and/or on the second master communication path to a subsequent switch, may set an error information for the corresponding telegram. Similarly, the network distributor adjacent to the interference, i.e. the network distributor that detects the interference, which may equally be a line interference, on the first master communication path and/or on the second master communication path to a subsequent switch, may set an error information for the corresponding telegram. 
     The error information may comprise changing the telegram address to an alternate telegram address. The master subscriber configures the switch or the corresponding network distributor such that the telegram path for normal operation is set, as well as an alternative telegram path for error operation, wherein setting the telegram path for normal operation comprises assigning the switching ports or the distribution ports to the telegram address for outputting the telegram. Furthermore, setting the alternative telegram path e.g. comprises changing the telegram address to the alternative telegram address, via which the fault that has occurred may be indicated, and assigning the switching ports or the distribution ports to the changed telegram address for outputting the telegram. 
     In a further embodiment, the network distributor adjacent to an interference and/or the switch adjacent to an interference and/or a slave subscriber adjacent to an interference are embodied in error mode, provided that the first telegram already has the first error information and/or the second telegram already has the second error information, to discard the first telegram with the first error information and/or the second telegram with the second error information. By discarding a telegram when an error information has already been detected in the corresponding telegram, it may be avoided in an advantageous way that the respective telegram circulates in the automation network and takes up unnecessary capacity as well as occupies the transmission medium. In particular, the network distributor adjacent to an interference and/or the switch adjacent to an interference and/or the slave subscriber adjacent to an interference may herein be used advantageously to detect a line interference in the automation network. 
     In a further embodiment, a slave subscriber is arranged between a first switch and a second switch and/or between a first network distributor and a second network distributor. In error mode, the slave subscriber is embodied to set the first error information for the first telegram and/or the second error information for the second telegram and to return the first telegram with the first error information to the master subscriber via the second master communication path and/or the second telegram with the second error information back to the master subscriber via the first master communication path. This allows a flexible embodiment of the automation network, since the slave subscriber may also be arranged between two neighboring switches as well as between two neighboring network distributors. In an advantageous manner, a slave subscriber may also be embodied to set the error information, which may be implemented in a similar manner to the above explanation, i.e. e.g. by changing the telegram address. 
     In a further embodiment, the switch and the slave subscriber detect an interference on the first master communication path and/or on the second master communication path and/or on the first slave communication path and/or on the second slave communication path and initiate error mode. Furthermore, it is conceivable that a network distributor is also embodied to detect the interference on the first master communication path and/or on the second master communication path and/or on the first slave communication path and/or on the second slave communication path and to trigger the error mode. In an advantageous manner, both the switch and a slave subscriber are embodied to initiate the error mode by setting the error information in the corresponding telegram, provided that a line interference, e.g. an interruption, has been detected. This feature may be equally fulfilled by a network subscriber. 
     In a further embodiment, the first telegram and the second telegram are each embodied as EtherCAT telegrams. The known EtherCAT standard may advantageously be used, provided that the telegrams are embodied as EtherCAT telegrams. In particular, the real-time capability of the automation network may be ensured by using the real-time capable data transmission protocol. 
     The advantageous embodiments and further embodiments of the invention described above and/or indicated in the subclaims may be used individually or in any combination with one another—except, for example, in cases of clear dependencies or incompatible alternatives. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-described properties, features and advantages of the present invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of embodiments, which will be described in more detail in connection with the schematic drawings, in which: 
         FIG. 1  shows a schematic structure of an automation network with network subscribers according to a first embodiment; 
         FIG. 2  shows a schematic structure of an automation network with network subscribers according to a second embodiment; 
         FIG. 3  shows a schematic structure of an automation network with network subscribers according to a third embodiment; and 
         FIG. 4  shows a schematic structure of an automation network with network subscribers according to a fourth embodiment. 
     
    
    
     It is to be noted that the figures are merely schematic in nature and not to scale. In this sense, components and elements shown in the figures may be exaggeratedly large or reduced in size for better understanding. Furthermore, it is pointed out that the reference numerals in the figures have been chosen to remain unchanged if the elements and/or components are of the same embodiment. 
     DETAILED DESCRIPTION 
     Automation networks  100  are usually implemented as field-bus systems in which the network subscribers  200  are interconnected via the field bus. The automation network  100  may comprise a master subscriber  205 , at least a switch  210 , and a plurality of slave subscribers  215 . The master subscriber  205  may be connected to the switch  210  and the switch  210  may be connected to the plurality of slave subscribers  215  via a redundant data line network, wherein the redundant data line network may e.g. comprise two physical transmission media, for transmitting a first telegram  220  and a second telegram  225  of the master subscriber  205  to the switch  210  and to the plurality of slave subscribers  215  in opposite directions. The redundant data line network may ensure that the master subscriber  205  may continue to communicate with all slave subscribers  215 , in particular during error mode, e.g. due to a physical interruption of the transmission medium. 
     The proposed automation network and the methods for data transmitting in the network are in the following described by way of example on the basis of the real-time capable EtherCAT protocol and is not limited to a master-slave hierarchy. 
     In the following, the term “on the fly” is understood to mean that a processor of a slave subscriber  215  is embodied to start processing a telegram before the telegram has been completely received via a first slave port  600  of the slave subscriber  215 . Where reference is made in the following to processing a telegram in passing, this includes reading out the output data addressed to the respective slave subscriber  215 , as well as inserting input data into the telegram and, in normal operation of the automation network  100 , forwarding the telegram to the subsequent slave subscriber  215 . 
     In the following, the term “normal operation” is understood to mean the state or mode of operation of the automation network  100  in which no interference occurs. 
     In the following, the term “error mode” refers to the state or mode of operation of the automation network  100  in which a line interference, which may be in the form of a physical interruption of the transmission medium, occurs in the automation network  100  and which impedes continuous communication of the master subscriber  205  with the slave subscribers  215 . 
     In the following, a first telegram  220 , a second telegram  225 , a third telegram  282  and a fourth telegram  284  are each understood as an EtherCAT telegram, i.e. the real-time capable protocol on which the telegrams are based is the EtherCAT protocol. An EtherCAT telegram is embedded in an Ethernet data telegram and therefore has the Ethernet data telegram format structure according to the IEEE 802.3 standard or with a tag field according to the IEEE 802.1Q standard. If in the following, only one of the above-mentioned telegrams or a telegram or an EtherCAT telegram is mentioned, the Ethernet data telegram or the data telegram is included. 
     The core idea of the present automation network and methods for data transmitting in the automation network lies in providing a method and an automation network  100  with network subscribers  200 , which, when using at least one switch  210  and a redundant data line network, allows the telegrams of the master subscriber  205  to be returned to the master subscriber  205  by the slave subscribers  215  and/or by the switch  210  in error mode, i.e. in the event of a physical interruption of the transmission medium, and communication of the master subscriber  205  with all other network subscribers  200  may thereby be guaranteed. 
     The structure and functionality of the automation network  100  is described below with reference to  FIGS. 1 to 4 , with the associated reference numerals from the four figures being used in the description where useful and necessary. 
       FIG. 1  shows an automation network  100  comprising a plurality of network subscribers  200 , wherein at least one network subscriber  200  may be configured as a master subscriber  205 , at least one network subscriber  200  may be configured as a switch  210 , and a plurality of network subscribers  200  may be configured as slave subscribers  215 . For example, a slave subscriber  215  is shown in  FIG. 1 . The master subscriber  205  comprises a first master port  400  and a second master port  415 , and the switch  210  comprises a first switching port  500  and a second switching port  515  and a third switching port  530  and a fourth switching port  550 . The slave subscriber  215  comprises a first slave port  600  and a second slave port  620 , each of said ports comprising a transmitter TX for transmitting telegrams and a receiver RX for receiving telegrams. 
     The transmitter TX of the first master port  400  is connected to the receiver RX of the first switching port  500  via a first master communication path  310 . Furthermore, the transmitter TX of the second switching port  515  is connected to the receiver RX of the second master port  415  via the first master communication path  310 . The transmitter TX of the second master port  415  is connected to the receiver RX of the second switching port  515  via a second master communication path  315 . Moreover, the transmitter TX of the first switching port  500  is connected to the receiver RX of the first master port  400  via the second master communication path  315 . Accordingly, the master subscriber  205  forms a first dual ring structure  300  via the first master port  400  as well as the second master port  415  with the first master communication path  310  as well as with the second master communication path  315  and the first switching port  500  as well as the second switching port  515  of the switch  210 . 
     Furthermore, the transmitter TX of the third switching port  530  is connected to the receiver RX of the first slave port  600  via a first slave communication path  320 . The transmitter TX of the second slave port  620  is connected to the receiver RX of the fourth switching port  550  via the first slave communication path  320 . The transmitter TX of the first slave port  600  is further connected to the receiver RX of the third switching port  530  via a second slave communication path  325 . Similarly, the transmitter TX of the fourth switching port  550  is connected to the receiver RX of the second slave port  620  via the second slave communication path  325 . The slave subscriber  215  forms a second dual ring structure  305  with the switch  210  via the first slave port  600 , via the second slave port  620 , via the first slave communication path  320 , and via the second slave communication path  325 . 
     The master subscriber  205  is embodied to send two telegrams based on the same data packet. For this purpose, the master subscriber  205  outputs a first telegram  220  to the receiver RX of the first switching port  500  via the transmitter TX of the first master port  400  via the first master communication path  310 . The switch  210  is embodied to receive the first telegram  220  via the receiver RX of the first switching port  500 . Further, the switch  210  is embodied to output the first telegram  220  to the receiver RX of the first slave port via the transmitter TX of the third switching port  530  via the first slave communication path  320 . The slave subscriber  215  is embodied to process the first telegram  220  on the fly. 
     The slave subscriber  215 , after processing the first telegram  220 , is embodied to output the first telegram  220  to the receiver RX of the fourth switching port  550  via the transmitter TX of the second slave port  620  via the first slave communication path  320 . The switch  210  is embodied to receive the first telegram  220  via the receiver RX of the fourth switching port  550 , and to transmit it via the transmitter TX of the second switching port  515  via the first master communication path  310  to the receiver RX of the second master port  415 . Finally, the master subscriber  205  is configured to receive the first telegram  220  via the receiver TX of the second master port  415 . Furthermore, the master subscriber  205  may be embodied to evaluate the first telegram  220 . 
     The master subscriber  205  is further embodied to output a second telegram  225  to the receiver RX of the second switching port  515  via the transmitter TX of the second master port  415  via the second master communication path  315 . The switch  210  is configured to receive the second telegram  225  via the receiver RX of the second switching port, and to output the second telegram  225  via the transmitter TX of the fourth switching port  550  via the second slave communication path  325  to the receiver RX of the second slave port  620 . For example, the slave subscriber  215  is not embodied to process the second telegram  225  received by the slave subscriber  215  via the receiver RX of the second slave port  620 . However, the slave subscriber  215  is embodied to output the second telegram  225  to the receiver RX of the third switching port  530  via the transmitter TX of the first slave port  600  via the second slave communication path  325 . The receiver RX of the third switching port  530  is embodied to receive the second telegram  225 . The switch  210  is further configured to output the second telegram  225  to the receiver RX of the first master port  400  via the transmitter TX of the first switching port  500  via the second master communication path  315 . 
     The master subscriber  205  is embodied to receive the second telegram  225  via the receiver RX of the first master port  400 . Furthermore, the master subscriber  205  may be configured to discard one of the two telegrams, i.e. the first telegram  220  or the second telegram  225 . For example, in said embodiment example, the master subscriber  205  may discard the second telegram  225  because the slave subscriber  215  did not process the second telegram  225  on the fly. The master subscriber  205  may, as an alternative to discarding one of the two telegrams, be configured in a read operation to or-link, i.e. to overlay the data in the user data fields of the two telegrams. An or-operation, due to the superposition of the data in the user data fields of the telegrams received by the master subscriber  205  via the first master communication path  310  and via the second master communication path  315  from the slave subscriber  215  or a chain of slave subscribers, may serve to form a common telegram internally in the master subscriber  205 . 
       FIG. 1  thus shows the automation network  100  in normal operation, normal operation being characterized by the fact that the telegram traffic in the automation network  100  runs without interference. The depiction of the automation network  100  shown in  FIG. 1  with its network subscribers  200  has been chosen as an example, and does not limit the scope of protection to the depiction shown. The automation network  100  could alternatively deviate from the depiction and comprise network subscribers  200 . The terms RX and TX in  FIG. 1  generally refer to a receiver RX (RX: “receiver” or “receive”) and a transmitter TX (TX: “transceiver” or “transceive”). 
     For example, the first master communication path  310  may be implemented in the form of a first data line, and the second master communication path  315  may be implemented in the form of a second data line. It is conceivable to implement the first slave communication path  320  in the form of a third data line and the second slave communication path  325  in the form of a fourth data line. However, the described embodiment is only exemplary and may also be implemented in alternative ways. 
     For the sake of clarity, the following figures do not show the transmitters TX and the receivers RX of the individual ports of the network subscribers  200 . Nevertheless, the ports of the network subscribers  200  shown in  FIGS. 2 to 4  each have a transmitter TX for transmitting the telegrams and a receiver RX for receiving the telegrams. 
       FIG. 2  shows an extension of the automation network  100  shown in  FIG. 1 . The automation network  100  in  FIG. 2  also comprises the master subscriber  205 . Furthermore, the automation network  100  in  FIG. 2  comprises two switches  210  as a first switch  240  and a second switch  245 . In addition, the automation network  100  comprises six slave subscribers  215  as a first slave subscriber  260 , a second slave subscriber  262 , a third slave subscriber  264 , a fourth slave subscriber  266 , a fifth slave subscriber  268  and a sixth slave subscriber  270 . 
     The first slave subscriber  260  to sixth slave subscriber  270  are arranged in a chain. The first slave subscriber  260  to the sixth slave subscriber  270  each have the first slave port  600  and the second slave port  620 , via which the individual slave subscribers  215  are each connected to one another via the redundant data line network. An exception to the connection of the slave subscribers  215  via the first slave port  600  and via the second slave port  620  is e.g. provided for the section between the fourth slave subscriber  266  and the fifth slave subscriber  268 . For example, a first line interference  810  occurs between the fourth slave subscriber  266  and the fifth slave subscriber  268 , shown with the lightning bolt in  FIG. 2 . The first line interference  810  may be a physical interruption of the connection, i.e. the transmission medium, between the fourth slave subscriber  266  and the fifth slave subscriber  268 . 
     For example, in  FIG. 2  the first switch  240  and the second switch  245  each comprise two network distributors. For example, the first switch  240  comprises a first network distributor  230  and a second network distributor  235 . The second switch  245  may e.g. comprise a third network distributor  250  and a fourth network distributor  255 . Accordingly, a plurality of switches  210  may be provided in the automation network  100 , which may also be arranged in a chain like the slave subscribers  215  and may be connected to the first master port  400  as well as to the second master port  415  of the master subscriber  205  via the first master communication path  310  as well as via the second master communication path  315 . Furthermore, the automation network  100  in  FIG. 2  may also include other switches  210 . The first network distributor  230  to fourth network distributor  255  each include distribution ports. 
     For example, a first distribution port  700  of the first network distributor  230  corresponds to the first switching port  500  of the switch  210  shown in  FIG. 1 . For example, a second distribution port  705  of the first network distributor  230  corresponds to the third switching port  530  of the switch  210  shown in  FIG. 1 . For example, a second distribution port  710  of the second network distributor  235  may correspond to the fourth switching port  550  of the switch  210  shown in  FIG. 1 . Moreover, a third distribution port  715  of the second network distribution device  235  may correspond to the second switching port  515  in  FIG. 1 . Furthermore, the first network distributor  230  and the second network distributor  235  of the first switch  240  may be connected via a first internal connection  800 . In this, the first internal connection  800  may e.g. comprise a connection of the third switching port  707  of the first network switch  230  as well as the first switching port  708  of the second network switch  235 . 
     The first internal connection  800 , as well as the further internal connections described below, may be similarly configured to embody the line connection for the first master communication path  310  or for the second master communication path  315  or for the first slave communication path  320  or for the second slave communication path  325 , as well as for the further slave communication paths explained below, as cable lines, for example, in the form of copper lines, fiber optic lines, or the like. Also, the embodiment of the line connections and the quality of the line redundancy is not dependent on the arrangement of the individual network subscribers  200 . 
     The first switch  240  may be connected to the second switch  245  via the third distribution port  715  of the second network distribution device  235 , as well as via the first master communication path  310  and via the second master communication path  315 , wherein the connection of the third distribution port  715  of the second network distribution device  235  comprises the connection to the first distribution port  720  of the third network distribution device  250 . 
     The third network distributor  250  may be connected to a placeholder X via the second distribution port  725  of the third network distributor  250  via a third slave communication path  335  as well as via a fourth slave communication path  340 . Similarly, the fourth network distributor  255  may be connected to the placeholder X via the second distribution port  740  of the fourth network distributor  255  via the third slave communication path  335  as well as via the fourth slave communication path  340 . Here, the placeholder X is representative of a slave subscriber  215  and/or a chain of slave subscribers  215  that may be connected to the second switch  245  via the third slave communication path  335  as well as via the fourth slave communication path  340 . 
     The third network distributor  250  may be connected to a first distribution port  735  of the fourth network distributor  255  via the third distribution port  730  of the third network distributor  250  via a second internal connection  805 . Since the second switch  245  may be embodied similarly to the first switch  240 , the first distribution port  720  of the third network distributor  250  as well as the second distribution port  725  of the third network distributor  250  may be embodied like the second distribution port  740  of the fourth network distributor  255  and the third distribution port  745  of the fourth network distributor  255  may be embodied like the first switch  240  as explained above. For this reason, reference is made to the above description. The fourth network distributor  255  of the second switch  245  is connected to the second master port  415  of the master subscriber  205  via the third distribution port  745  of the fourth network distributor  255  via the first master communication path  310  and via the second master communication path  315 . 
     The chain of slave subscribers  215  is connected to the first slave port  600  of the first slave subscriber  260  via the first slave communication path  320  and via the second slave communication path  325  to the second distribution port  705  of the first network distributor  230 . Furthermore, the last slave subscriber  215  in the chain, that is, the sixth slave subscriber  270  is connected to the second distribution port  710  of the second network distributor  235  via the second slave port  620  through the first slave communication path  320  and via the second slave communication path  325 . 
     In contrast to the description for  FIG. 1 , the master subscriber  205  in  FIG. 2  may e.g. be embodied to specify to the first switching center  240  and the second switching center  245 , for example by prior configuration, via which distribution port of the first network distributor  230  and via which distribution port of the second network distributor  235  and via which distribution port of the third network distributor  250  and finally via which distribution port of the fourth network distributor  255  the first network distributor  230  to fourth network distributor  255  has to output a telegram from the master subscriber  205 . The first network distributor  230  to the fourth network distributor  255  may e.g. store this setting in the routing table of the respective network distributor in order to then access the stored routing information for the output of the respective telegram via the assigned distribution port when a telegram is received. 
     In an alternative embodiment, a telegram from the master subscriber  205  may also comprise address information indicating which distribution port the corresponding network distributor is to route a telegram. The address information of a telegram may e.g. be located in the header portion of the telegram in order to make a routing decision as quickly as possible. For example, the master subscriber  205  may be configured to output a first telegram  220  to the first distribution port  700  of the first network distributor  230  via the first master communication path  310 . The first network distributor  230  forwards the first telegram  220  to the first slave port  600  of the first slave subscriber  260  via the second distribution port  705  of the first network distributor  230  via the first slave communication path  320 . 
     Receiving the first telegram  220  via the first distribution port  700  of the first network distributor  230  and outputting the first telegram  220  via the second distribution port  705  of the first network distributor  230  may have been set by the master subscriber  205 , e.g. prior to sending the first telegram  220  in the first network distributor  230 . The first telegram  220  may have a target address, which may be located, for example, in the header portion of the first telegram  220 . The target address may e.g. be embodied as a so-called ELAN ID. For the first telegram  220 , the ELAN ID may comprise the value 1. The first slave subscriber  260  forwards the first telegram  220  with the ELAN ID 1 via the second slave port  620  of the first slave subscriber  260  to the first slave port  600  of the second slave subscriber  262  via the first slave communication path  320 . The first slave subscriber  260  processes the first telegram  220  on the fly and forwards the first telegram  220 , and similarly the second slave subscriber  262  forwards the first telegram  220  after processing by the second slave subscriber  262  via the second slave port  620  of the second slave subscriber  262  via the first slave communication path  320  to the first slave port  600  of the third slave subscriber  264 . 
     The third slave subscriber  264  processes the first telegram  220  on the fly and forwards the first telegram  220  to the first slave port  600  of the fourth slave subscriber  266  via the second slave port  620  of the third slave subscriber  264  via the first slave communication path  310 . The fourth slave subscriber  266  processes the first telegram  220  on the fly, as well. For example, the fourth slave subscriber  266  may not forward the first telegram  220  to the fifth slave subscriber  268  after processing in passing due to the first line interference  810 , which may include an interruption of the first slave communication path  320 . 
     Due to the first line interference  810 , the fourth slave subscriber  266  initiates error mode and couples the first telegram  220  having the ELAN ID 1 back to the third slave subscriber  264  via the second slave communication path  325 . The internal feedback of the first telegram  220  in the fourth slave subscriber  266 , i.e. a short circuit of the transmitter with the receiver of the second slave port  620  of the fourth slave subscriber  266  may e.g. be caused by a short circuit shown in  FIG. 2  in the fourth slave subscriber  266  or, respectively, in the other slave subscribers, which comprises, for example, a first multiplexer and a second multiplexer, wherein the first multiplexer and the second multiplexer may be embodied to internally short-circuit the transmitter with the receiver of the corresponding slave port, respectively, so that the telegram may be sent back to the master subscriber  205  via the other slave communication path. 
     The fourth slave subscriber  266  sends the first telegram  220  with the ELAN ID 1 via the first slave port  600  of the fourth slave subscriber  266  and via the second slave communication path  325  to the second slave port  620  of the third slave subscriber  264 . The third slave subscriber  264  now no longer processes the first telegram  220  with the ELAN ID 1, but sends the first telegram  220  via the first slave port  600  of the third slave subscriber  264  and via the second slave communication path  325  to the second slave port  620  of the second slave subscriber  262 . The second slave subscriber  262  is also not embodied to process the first telegram  220  again, either. The second slave subscriber  262  transmits the first telegram  220  via the first slave port  600  of the second slave subscriber  262  and via the second slave communication path  325  to the second slave port  620  of the first slave subscriber  260 . However, the first slave subscriber  260  is again not configured to reprocess the first telegram  220 . 
     The first slave subscriber  260  outputs the first telegram  220  via the first slave port  600  of the first slave subscriber  260  and via the second slave communication path  325  to the second distribution port  705  of the first network distributor  230 . The first network distributor  230  outputs the first telegram  220  to the first master port  400  of the master subscriber  205  via the first distribution port  700  of the first network distributor  230  and via the second master communication path  315 . The first network distributor  230  may output the first telegram  220  directly via the first distribution port  700  of the first network distributor  230  since e.g. the first telegram  220  has been preset by the master subscriber  205  to be received or output by the first network distributor  230  via the first distribution port  700  of the first network distributor  230  and via the second distribution port  705  of the first network distributor  230 , respectively. 
     For example, a second telegram  225  output by the master subscriber  205  via the second master port  415  and via the second master communication path  315  may comprise an ELAN ID 2, which may be included in the header portion of the second telegram  225 . It is conceivable that the master subscriber  205  may set for the third network distributor  250  and the fourth network distributor  255  that the third network distributor  250  and the fourth network distributor  255  each receive the second telegram  225  having the ELAN ID 2 via the third distribution port  745  of the fourth network distributor  255 , and the fourth network distributor  255  outputs the second telegram  225  via the first distribution port  735  of the fourth network distributor  255  to the third distribution port  730  of the third network distributor  250  via a second internal connection  805 . The second network distributor  250  may output the second telegram  225  to the third distribution port  715  of the second network distributor  235  via the first distribution port  720  of the third network distributor  250  over the second master communication path  315 . The second network distributor  235  may output the second telegram  225  to the second slave port  620  of the sixth slave subscriber  270  via the second distribution port  710  of the second network distributor  235  via the second slave communication path  325 . 
     In this regard, as explained above, the master subscriber  205  may preset for the second network distributor  235  that the second network distributor  235  receives the second telegram  225  via the third distribution port  715  of the second network distributor  235  and forwards it via the second distribution port  710  of the second network distributor  235 . The sixth slave subscriber  270  forwards the second telegram  225  to the second slave port  620  of the fifth slave subscriber  268  via the first slave port  600  of the sixth slave subscriber  270  over the second slave communication path  325 . Since the second slave communication path  325  between the fifth slave subscriber  268  and the fourth slave subscriber  266  is interrupted, e.g. by the first line interference  810 , the fifth slave subscriber  268  cannot forward the second telegram  225  to the fourth slave subscriber  266 . For this reason, the fifth slave subscriber  268  triggers the error mode, just as the fourth slave subscriber  266  has already done for the first telegram  220 . 
     Also, the fifth slave subscriber  268  may have a coupling device comprising a first multiplexer and a second multiplexer to short-circuit the transmitter to the receiver of the first slave port  600  of the fifth slave subscriber  268  to feedback the second telegram  225  in the fifth slave subscriber  268  so that the fifth slave subscriber  268  may process the second telegram  225  on the fly after the short-circuit. The fifth slave subscriber  268  outputs the second telegram  225  to the adjacent slave subscriber, i.e. the sixth slave subscriber  270  in the example shown, via the first slave communication path  320  after processing it on the fly. 
     The sixth slave subscriber  270  receives the second telegram  225  via the first slave port  600  of the sixth slave subscriber  270 , processes the second telegram  225  on the fly, and then outputs or receives the second telegram  225  via the second slave port  620  of the sixth slave subscriber  270  via the first slave communication path  320  to the second distribution port  710  of the second network distributor  235  from the second distribution port  710  of the second network distributor  235 . In addition, the second network distributor  235  may be configured to receive or output the third telegram with ELAN ID 3, and the fourth telegram with ELAN ID 4, via the first distribution port  708  of the second network distributor  235  and via the third distribution port  715  of the second network distributor  235 , respectively. 
     Furthermore, the configuration of the third network distributor  250  may provide that the third network distributor  250  receives or outputs the first telegram  220  with the ELAN ID 1 and the second telegram  225  with the ELAN ID 2 respectively via the first distribution port  720  of the third network distributor  250  and via the third distribution port  730  of the third network distributor  250 . Furthermore, the third network distributor  250  may be configured to receive or output the third telegram with the ELAN ID 3, and the fourth telegram with the ELAN ID 4, via the first distribution port  720  of the third network distributor  250  and via the second distribution port  725  of the third network distributor  250 , respectively. 
     A setting of the fourth network distributor  255  may mean that the fourth network distributor  255  receives or outputs the first telegram  220  with the ELAN ID 1 and the second telegram  225  with the ELAN ID 2 via the first distribution port  735  of the fourth network distributor  255  and via the third distribution port  745  of the fourth network distributor  255 , respectively. Furthermore, the fourth network distributor  255  may receive or output the third telegram with ELAN ID 3, and the fourth telegram with ELAN ID 4, via the third distribution port  745  of the fourth network distributor  255  and via the second distribution port  740  of the fourth network distributor  255 , respectively. In the automation network  100 , the aforementioned configurations of the first network distributor  230  to fourth network distributor  255  allow the master subscriber  205  to receive the first telegram  220 , the second telegram  225 , as well as the third telegram to the placeholder X, and the fourth telegram to the placeholder X, back despite a line interference, and the master subscriber  205  thereby reaches all other network subscribers  200 , in particular those that are adjacent to the first line interference  810 . 
     The routing of the first telegram  220  and the second telegram  225  through the first network distributor  230  to the fourth network distributor  525  described in  FIG. 2  is based on ELAN IDs, which the first telegram  220  and the second telegram  225  each comprise. The ELAN IDs may be formed in a similar way to VLAN IDs and may be located in a tag field of a telegram, wherein a telegram is preferably embodied in the form of an EtherCAT telegram. 
     If the routing of the telegrams in the automation network  100  in  FIG. 2  is e.g. based on a routing with MAC addresses (MAC: Media Access Control), then the first master port  400  e.g. comprises the MAC address MAC20 and the second master port  415  e.g. comprises the MAC address MAC10. The first telegram  220  may then have a first MAC address MAC1 and the second telegram  225 , which the master subscriber  205  outputs via the second master port  415 , may comprise a second MAC address MAC2. If the master subscriber  205  outputs the third telegram via the first master port  400 , the third telegram may e.g. comprise a third MAC address MAC3. Furthermore, the master subscriber  205  may output the fourth telegram via the second master port  415 , having a fourth MAC address MAC4. The master subscriber  205  may set the first network distributor  230  to fourth network distributor  255  such that, for example, when the first network distributor  230  receives the second telegram  225  via the second distribution port  705  of the first network distributor  230 , the second MAC address MAC2 of the second telegram  225  is set to the MAC address MAC20 of the first master port  400 . 
     Furthermore, the master subscriber  205  may configure the second network distributor  235  to set the first MAC address MAC to the MAC address MAC10 of the second master port  415  upon receiving the first telegram  220  with the first MAC address MAC11 via the second distribution port  710  of the second network distributor  235 . Furthermore, the master subscriber  205  may configure the third network distributor  250  to set the third network distributor  250  to the MAC address MAC20 of the first master port  400  of the master subscriber  205  upon receiving the fourth telegram with a fourth MAC address MAC4 via the second distribution port  725  of the third network distributor  250 . The fourth network distributor  255  may be set by the master subscriber  205  in such a way that the fourth network distributor  255  sets the third MAC address MAC3 of the third telegram to the MAC address MAC10 of the second master port  415  of the master subscriber  205  upon receiving the third telegram with the third MAC address MAC3 via the second distribution port  740  of the fourth network distributor  255 . The MAC addresses mentioned respectively refer to the target addresses of the individual telegrams. 
     As an alternative to routing the telegrams via MAC addresses, routing the telegrams via destination IDs using a so-called ROUT-TAG tag field or VLAN IDs using a VLAN-TAG tag field is also conceivable, although this is not described. 
     The above description for the setting of the first network distributor  230  to the fourth network distributor  255  with respect to the receipt of the first telegram  220  as well as the second telegram  225  and the third telegram or the fourth telegram referred to the change of the MAC address with respect to the target MAC address corresponding to the respective MAC address of the first master port  400  and the second master port  415 , respectively, since the first telegram  220  as well as the second telegram  225  and the third telegram as well as the fourth telegram in normal operation respectively correspond to the first master port  400  with the MAC address MAC20 and the second master port  415  with the MAC address MAC20. 
     Now, if the first line interference  810  occurs between the fourth slave subscriber  266  and the fifth slave subscriber  268  on the first slave communication path  320  as well as on the second slave communication path  325 , the first telegram  220  reaches the first network distributor  230  via the second slave communication path  325 . The first network distributor  230  is configured to receive the first telegram  220  via the second distribution port  705  of the first network distributor  230 , and to set the first MAC address MAC1 to the MAC address MAC20 of the first master port  400 . Furthermore, the first network distributor  230  outputs the first telegram  220  to the master subscriber  205  via the first distribution port  700  of the first network distributor  230  and via the second master communication path  315 . The master subscriber  205  receives the first telegram  220  via the first master port  400 , which has the MAC address MAC20. 
     The second telegram  225  issued by the master subscriber  205  via the second master port  415  and the second master communication path  315  reaches the second network distributor  235  after the second telegram  225  is fed back due to the first line interference  810  via the first slave communication path  320  and via the second distribution port  710  of the second network distributor  235 . The second network distributor  235  is configured to set the second MAC address MAC2 of the second telegram  225  to the MAC address MAC10 of the second master port  415 , such that the second network distributor  235  outputs the second telegram  225  to the second switch  245  via the third distribution port  715  of the second network distributor  235  and the first master communication path  310 . 
     The second switch  245  including the third network distributor  250  and the fourth network distributor  255  is configured to output the second telegram  225  to the second master port  415  of the master subscriber  205  having the MAC address MAC10, via the third distribution port  745  of the fourth network distributor  255  and the first master communication path  310 . For example, the first line interference  810  does not affect the telegram path of the third telegram and the fourth telegram, so that the previous settings for the third telegram having the third MAC address MAC3 in the fourth network distributor  255  and the setting for the fourth telegram with the fourth MAC address MAC4 in the third network distributor  250  still apply. 
       FIG. 3  shows an extension of the automation network  100  shown in  FIGS. 1 and 2 . In contrast to the automation network  100  with network subscribers  200  shown in  FIGS. 1 and 2 , the telegram traffic based on the output of the third telegram  282  with the ELAN ID 3 via the first master port  400  of the master subscriber  205  and of the fourth telegram  284  with the ELAN ID 4 via the second master port  415  is referred to below in  FIG. 3 —at first for the normal operation, in which no line interference occurs. The master subscriber  205  is embodied to output the third telegram  282  having the ELAN ID 3 to the first switch  240  via the first master communication path  310 , wherein the first switch  240  comprises the first network distributor  230  and the second network distributor  235 . The first network distributor  230  is configured to receive the third telegram  282  via the first distribution port  700  of the first network distributor  230 , and to output the third telegram  282  via the third distribution port  707  of the first network distributor  230  to the first distribution port  708  of the second network distributor  235  via the first internal connection  800 . 
     The second network distributor  235  is configured to forward the third telegram  282  to the second switch  245  via the third distribution port  715  of the second network distributor  235  via the first master communication path  310 , the second switch  245  comprising the third network distributor  250  and the fourth network distributor  255 . The third network distributor  250  receives the third telegram  282  via the first distribution port  720  of the third network distributor  250  and outputs the third telegram  282  to a seventh slave subscriber  272  via a third slave communication path  335 . The seventh slave subscriber  272  is configured to receive the third telegram  282  via the first slave port  600  of the seventh slave subscriber  272 , to process the third telegram  282  on the fly, and to forward the third telegram  282  via the second slave port  620  of the seventh slave subscriber  272  to the eighth slave subscriber  274  via the third slave communication path  335 . The eighth slave subscriber  274  is configured to receive the third telegram  282  via the first slave port  600  of the eighth slave subscriber  274 , to process the third telegram  282  on the fly, and to output the third telegram  282  to the ninth slave subscriber  276  via the second distribution port  620  of the eighth slave subscriber  274  via the third slave communication path  335 . 
     The ninth slave subscriber  276  receives the third telegram  282  via the first slave port  600  of the ninth slave subscriber  276 , processes the third telegram  282  on the fly similar to the previous slave subscribers, and outputs the third telegram  282  to the tenth slave subscriber  278  via the second slave port  620  of the ninth slave subscriber  276  via the third slave communication path  335 . The tenth slave subscriber  278  is configured to receive the third telegram  282  via the first slave port  600  of the tenth slave subscriber  278 , to process the third telegram  282  on the fly, and to forward the third telegram  282  via the second slave port  620  of the tenth slave subscriber  278  to the fourth network distributor  255  via the third slave communication path  335 . The fourth network distributor  255  is configured to receive the third telegram  282  via the second distribution port  740  of the fourth network distributor  255 , and to forward the third telegram  282  via the third distribution port  745  of the fourth network distributor  255  to the master subscriber  205  via the first master communication path  310 . The master subscriber  205  receives the third telegram  282  via the second master port  415 . 
     Furthermore, the master subscriber  205  is configured to output the fourth telegram  284  to the second switch  245  via the second master communication path  315 . The fourth network distributor  255  of the second switch  245  receives the fourth telegram  284  with the ELAN ID 4 via the third distribution port  745  of the fourth network distributor  255 , and forwards the fourth telegram  284  to the tenth slave subscriber  278  via the second distribution port  740  of the fourth network distributor  255  and the fourth slave communication path  340 . The tenth slave subscriber  278  receives the fourth telegram  284  via the second slave port  620  of the tenth slave subscriber  278  and forwards it to the ninth slave subscriber  276  via the first slave port  600  of the tenth slave subscriber  278  without any processing. The ninth slave subscriber  276  receives the fourth telegram  284  via the second slave port  620  of the ninth slave subscriber  276  and forwards the fourth telegram  284  via the first slave port  600  of the ninth slave subscriber  276  and the fourth slave communication path  340  to the eighth slave subscriber  274  without processing. 
     The eighth slave subscriber  274  receives the fourth telegram  284  via the second slave port  620  of the eighth slave subscriber  274  and forwards it directly (without processing) to the seventh slave subscriber  272  via the first slave port  600  of the eighth slave subscriber  274  and via the fourth slave communication path  340 . The seventh slave subscriber  272  receives the fourth telegram  284  via the second slave port  620  of the seventh slave subscriber  272  and outputs it to the third network distributor  250  via the first slave port  600  of the seventh slave subscriber  272  and the fourth slave communication path  340 . The third network distributor  250  receives the fourth telegram  284  via the second distribution port  725  of the third network distributor  250  and outputs the fourth telegram  284  to the first switch  240  via the first distribution port  720  of the third network distributor  250  via the second master communication path  315 . The first switch  240  is configured to receive the fourth telegram  284  via the second network distributor  235 . The second network distribution device  235  receives the fourth telegram  284  via the third distribution port  715  of the second network distributor  235  and forwards it to the third distribution port  707  of the first network distribution device  230  via the first distribution port  708  of the second network distribution device  235  and the first internal connection  800 . 
     The first network distributor  230  outputs the fourth telegram  284  to the first master port  400  of the master subscriber  205  via the second master communication path  315 . The previous description referred to normal operation, that is, the telegram traffic or telegram path of the third telegram  282  as well as the fourth telegram  284  without a line interference having occurred. The master subscriber  205  receives the fourth telegram  284  via the first master port  400  and is in normal operation embodied to discard the fourth telegram  284  and to evaluate only the third telegram  282  that has been processed by the slave subscribers on the fly, since the telegrams originate from the identical data packet. 
     Also, the explained third slave communication path  335  forms a dual ring structure with the fourth slave communication path  340  between the second distribution port  725  of the third network distributor  250  and the second distribution port  740  of the fourth network distributor  745 . 
     Furthermore, telegram traffic of the master subscriber  205 , which has been described in connection with the telegram traffic described in  FIGS. 1 and 2 , may be implemented in a similar manner using the first telegram  220  and the second telegram  225 , without limiting the scope of protection. The placeholder X, which in  FIG. 3  is exemplarily connected to the first network distributor  230  as well as to the second network distributor  235  via the first slave communication path  320  and via the second slave communication path  325 , may be representative of a slave subscriber and/or of a chain of slave subscribers as connected e.g. to the third network distributor  250  and to the fourth network distributor  255  via the third slave communication path  335  and via the fourth slave communication path  340 . For example, the slave subscriber  215  or the chain of slave subscribers represented by the placeholder X may be addressed via the first telegram  220  and the second telegram  225 . 
     After describing the normal operation explained above in connection with Fig., reference is now made to the error mode of the automation network  100  shown in  FIG. 3 . If, for example, as shown in  FIG. 3 , a second line interference  815  occurs between the first switch  240  and the second switch  245  on the first master communication path  310  and the second master communication path  315 , respectively, the third telegram  282  as well as the fourth telegram  284  cannot be routed without further ado, i.e. without changes to be made in the automation network  100 . 
     Similarly, the first and second telegrams may take the telegram path described in  FIG. 2 , could not easily be routed in the automation network  100  due to the second line interference  815 . The second line interference  815  may be similar to the first line interference  810  in  FIG. 2  and may comprise a physical interruption of the data line or the transmission medium. If the adjacent switch, i.e. the first switch  240  and the second switch  245  in the example shown in  FIG. 3 , detects that there is no connection between the first switch  240  and the second switch  245 , i.e. the first master communication path  310  and the second master communication path  315  are interrupted, then both the first switch  240  and the second switch  245  are embodied to initiate error operation and to enter an error information in the third telegram  282  and in the fourth telegram  284 , respectively. Furthermore, each network distributor may also be embodied to initiate the error operation, since it is not mandatory that the first network distributor  230  and the second network distributor  235  of the first switch  240  and the third network distributor  250  and the fourth network distributor  255  of the second switch  245  are directly connected to each other. 
     The error information that the second network distributor  235  e.g. sets for the third distribution port  715  of the second network distributor  235 , as well as the third network distributor  250  sets for the first distribution port  720  of the third network distributor  250 , may e.g. be based in an alternative ELAN ID for said ports. For example, the alternative ELAN ID may be 0x403 (in hexadecimal) for ELAN ID 3, as well as the alternative ELAN ID may be 0x404 (in hexadecimal) for ELAN ID 4. For completeness, the alternative ELAN ID may be 0x401 (in hexadecimal system) for the first telegram  220  with ID 1, and the alternative ELAN ID may be 0x402 (in hexadecimal system) for the second telegram  225  having ELAN ID 2. The alternative ELAN IDs mentioned may be set for the individual network distributors for the first distribution port and the third distribution port, respectively, each of which would have a connection to an adjacent network distributor in normal operation, by the master subscriber  205 . 
     Consequently, the second network distributor  235  as well as the third network distributor  250  are each embodied to check whether an alternative route for the third telegram  282  as well as for the fourth telegram  284  is stored for said network distributors after the detection of the second line interference  815 , i.e. the interruption of the connection between the second network distributor  235  and the third network distributor  250 . For the alternate route of the third telegram  282 , the second network distributor  235  may be configured to forward the third telegram  282  to the first network distributor  230  via the first distribution port  708  of the second network distributor  235  and the first internal connection  800  after successfully checking for the alternate route. The first network distributor  230  receives the third telegram  282  via the third distribution port  707  of the first network distributor  230  and returns the third telegram  282  to the first master port  400  of the master subscriber  205  via the first distribution port  700  of the first network distributor  230  and the second master communication path  315 . The fourth telegram  284  is returned by the third network distributor  250  to the seventh slave subscriber  272  via the second distribution port  725  of the third network distributor  250  and via the first slave communication path  335 . 
     The seventh slave subscriber  272  receives the fourth telegram  284  via the first slave port  600  of the seventh slave subscriber  272 , processes the fourth telegram  284  on the fly, and outputs the fourth telegram  284  in the alternate telegram route via the second slave port  620  of the seventh slave subscriber  272  via the third slave communication path  335  to the eighth slave subscriber  274 . The eighth slave subscriber  274  receives the fourth telegram  284  via the first slave port  600  of the eighth slave subscriber  274 , processes the fourth telegram  284  on the fly, and forwards the fourth telegram  284  to the ninth slave subscriber  276  via the second slave port  620  of the eighth slave subscriber  274  and via the third slave communication path  335 . 
     The ninth slave subscriber  276  receives the fourth telegram  284  via the first slave port  600  of the ninth slave subscriber  276 , processes the fourth telegram  284  on the fly, and outputs the fourth telegram  284  to the tenth slave subscriber  278  via the second slave port  620  of the ninth slave subscriber  276  and the third slave communication path. The tenth slave subscriber  278  receives the fourth telegram  284  via the first slave port  600  of the tenth slave subscriber  278 , processes the fourth telegram  284  on the fly, and forwards the fourth telegram  284  to the fourth network distributor  255  via the second slave port  620  of the tenth slave subscriber  278  and the third slave communication path  335 . 
     The fourth network distributor  255  receives the fourth telegram  284  via the second distribution port  740  of the fourth network distributor  255  and returns the fourth telegram  284  to the master subscriber  205  via the third distribution port  745  of the fourth network distributor  255  and the first master communication path  310 . The master subscriber  205  receives the fourth telegram  284  via the second master port  415 . 
     As an alternative to setting the error information in the form of the alternative ELAN ID, as has been explained, a free bit in the telegram may also be used for the error information or for routing. If ELAN IDs are used for routing the telegrams as described, the telegrams, which are preferably embodied as EtherCAT telegrams, comprise a so-called ELAN-TAG tag field. The ELAN-TAG tag field may be similar to the VLAN-TAG tag field, but may contain additional information if the corresponding telegram has been fragmented. Fragmentation may e.g. be performed by any of the first to fourth network distributors  230 ,  235 ,  250 ,  255  shown in  FIG. 3 . The master subscriber  205  subsequently needs the additional information about the fragmentation when assembling the individual telegram fragments. Furthermore, a telegram that has an ELAN TAG tag field also has a so-called ELAN end TAG tag field in the telegram, i.e. a data field ahead of the checksum field that comprises information that will be explained in more detail later. The ELAN ID in the ELAN-TAG tag field e.g. comprises 12 bits with bit  11  in the ELAN-TAG tag field being set when the error information for the alternative ELAN ID is set, e.g. by the corresponding adjacent network distributor or the adjacent switch. 
     Alternatively, if MAC addresses are used for routing the telegrams in the automation network  100 , it generally applies that the respective network distributor is configured to set the MAC address of the telegram to the MAC address MAC10 of the second master port  415  for telegrams that the respective network distributor is to output via the first distribution port, so that the corresponding network distributor may send the telegram back to the master subscriber  205 . Similarly, the master subscriber  205  provides for the corresponding network distributors to set the MAC address of the telegram to the address MAC20, i.e. the MAC address of the first master port  400 , for telegrams that are to be output to the subsequent network subscriber  200  via the third distribution port in each case. The aforementioned settings generally enable the individual network distributors to send the telegrams back to the master subscriber  205  via the respective other master communication path even if a line interference is detected between the network distributors, that is, on the first master communication path  310  and on the second master communication path  315 . 
     Furthermore, the telegrams must have an additional identifier so that the master subscriber  205  or other network subscribers  200  in the automation network  100  may recognize that a line interference has occurred in the automation network  100  on one of the communication paths and the MAC address of a telegram that has already been exchanged must not be exchanged again, since the automation network  100  may be used advantageously for detecting a single line interference. For another line interference when the error information is already set, that is, when the alternative ELAN ID or alternative MAC address is already set, the slave subscribers as well as the network distributors are preferably embodied to discard the corresponding telegram. In the case of the ELAN ID for routing, no additional identifier is therefore required in the telegram to indicate that error operation has already been triggered. 
       FIG. 4  shows an alternative arrangement of the network subscribers  200  in the automation network  100 . For example, the basic structure of the arrangement of the network subscribers  200  in  FIG. 4  is similar to the arrangement of the network subscribers  200  in  FIG. 2 . Unlike the arrangement of network subscribers  200  in  FIG. 2 , where the first line interference  810  has occurred between the fourth slave subscriber  266  and the fifth slave subscriber  268 , in  FIG. 4 , for example, a third line interference  820  occurred between an eleventh slave subscriber  280  and the third network distributor  250  of the second switch  245 . The eleventh slave subscriber  280  is e.g. located between the first switch  240  and the second switch  245 , and the connection to the second switch  245  may be physically interrupted by said third line interference  820 . The eleventh slave subscriber  280  is connected to the third distribution port  715  of the second network distributor  235  via the first master communication path  310  and via the second master communication path  315  and via the first slave port  600  of the eleventh slave subscriber  280 . 
     For the connections of the other slave subscribers  215  or network subscribers  200  in the automation network  100  in  FIG. 4 , reference is made to the descriptions of the above figures and the features will not be repeated here. Furthermore, the features concerning the assignment of the alternative ELAN IDs or the MAC addresses for the individual ports of the network subscribers  200  in the automation network  100  shall not be repeated in  FIG. 4 . Likewise, the detailed description of the telegram traffic starting from the master subscriber  205  is not repeated. In the example shown in  FIG. 4 , the eleventh slave subscriber  280  is embodied to set the first error information in the first telegram  220  after the eleventh slave subscriber  280  has detected the third line interference  820  to the subsequent third network distributor  250 . In this context, the first error information may e.g. comprise setting the ELAN ID 1 to the alternative ELAN ID 0x401 (in the hexadecimal system). 
     Due to the short-circuited transmitter and receiver in the second slave port  620  of the eleventh slave subscriber  280 , the eleventh slave subscriber  280  is embodied to forward the first telegram  220  to the first switch  240  via the first slave port  600  of the eleventh slave subscriber  280  via the second master communication path  315 . The first switch  240  is embodied to receive the first telegram  220  with the alternate ELAN ID, as mentioned above, via the third distribution port  715  of the second network distributor  235 . The second network distribution device  235  outputs the first telegram  220  to the third distribution port  707  of the first network distribution device  230  via the first distribution port  708  of the second network distribution device  235  and the first internal connection  800 . The first network distributor  230  outputs the first telegram  220  to the first master port  400  of the master subscriber  205  via the first distribution port  700  of the first network distributor  230  and the second master communication path  315 . 
     Alternatively, if the first telegram  220  already e.g. comprised the first error information, that is, e.g. the alternate ELAN ID having a value of 0x401 (in the hexadecimal system), the eleventh slave subscriber  280  would be configured to discard the first telegram  220 , provided that the eleventh slave subscriber  280  detected the third line interference  820  to the subsequent third network distributor  250 . This is due to the fact that the automation network  100  is embodied to detect only one line interference, and when the second line interference occurs, the network subscribers  200  would be embodied to overwrite the previous first error information and thereby restore the first telegram  220  to its original state, so that the first telegram  220  would circulate in the automation network without the master subscriber  205  being able to determine that a line interference, i.e. an error case, has occurred in the automation network  100 . 
     A possible telegram structure of the first telegram  220 , the second telegram  225 , the third telegram  282  as well as of the fourth telegram  284 , which may each be in the form of EtherCAT telegrams, may be implemented according to the following Table 1, where Table 1 lists the corresponding number of bytes of a data field and/or a plurality of data fields and/or a tag field and/or a plurality of tag fields in the telegram as well as their meaning: 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Number of bytes of data or tag fields 
               
               
                 in a telegram, as well as their meaning 
               
            
           
           
               
               
            
               
                 Byte 
                 Meaning 
               
               
                   
               
               
                 0 to 5  
                 Target MAC address 
               
               
                  6 to 11 
                 Sender MAC address 
               
               
                 12 to 13 
                 Protocol identification (value: 0xB6FE) 
               
               
                 14 to 19 
                 ELAN TAG 
               
               
                   
                 “Type”, 4 bit (value: 0) 
               
               
                   
                 “Priority”, 3 bit 
               
               
                   
                 “FragAllowed”, 1 bit 
               
               
                   
                 “ELAN ID”, 12 bit 
               
               
                   
                 “Reserve”, 4 bit 
               
               
                   
                 “FragOffset”, 8 bit 
               
               
                   
                 “FrameNo”, 16 bit 
               
               
                 20 
                 Ethertype (value: 0x88A4) 
               
               
                 from 21 
                 Ethernet data section 
               
               
                 n 
                 Last byte of the Ethernet data section or 
               
               
                   
                 “Padding” or “Padding Length”. 
               
               
                 n + 1 
                 ELAN-END TAG, 1 byte 
               
               
                   
                 “FragFollows”, 1 bit 
               
               
                   
                 “NextPrio”, 3 bit 
               
               
                   
                 “Padding”, 1 bit 
               
               
                 (n + 1) to (n + 4) 
                 Checksum 
               
               
                   
               
            
           
         
       
     
     According to the IEEE 802.3 standard for the packet-oriented Ethernet data telegram format structure, an Ethernet data frame also has a preamble and a Start Frame Delimiter (SFD) data field, which are not included in Table 1. Nevertheless, the first telegram  220 , the second telegram  225 , the third telegram  282  and the fourth telegram  284  each include a preamble and a Start Frame Delimiter (SFD) field. 
     Also in the case that the routing of the first telegram  220 , the second telegram  225 , the third telegram  282  as well as of the fourth telegram  284  is based on the use of the ELAN TAG tag field and the routing based on ELAN IDs, the first telegram  220 , the second telegram  225 , the third telegram  282  as well as the fourth telegram  284  each comprise the target MAC data field with the target MAC address as well as the sender MAC data field with the sender MAC address of the receiving as well as the sending network subscriber  200 . 
     The protocol identification data field comprises the value 0xB6FE (in hexadecimal system), which is assigned to the ELAN-TAG tag field. Preferably, the ELAN-TAG tag field is used provided that the first telegram  220 , the second telegram  225 , the third telegram  282  as well as the fourth telegram  284  may be fragmented by the first network distributor  230 , the second network distributor  235 , the third network distributor  250  and/or the fourth network distributor  255 , since the ELAN-TAG tag field comprises the information about the fragmenting of the first telegram  220 , the second telegram  225 , the third telegram  282  as well as the fourth telegram  284 . For comparison, the protocol identification data field would have the value 0x8100 (in hexadecimal) if the tag field is formed as a VLAN TAG and comprises a VLAN ID for routing the first telegram  220 , the second telegram  225 , the third telegram  282  as well as the fourth telegram  284 . Preferably, the VLAN-TAG tag field would be used for the case of transmitting the telegrams without fragmentation in the automation network  100 . 
     The ELAN-TAG tag field comprises a 4-bit Type data field by which the ELAN-TAG tag field with the value zero is identified by default and where the values 1 to 3 are e.g. reserved for possible extensions. Furthermore, the ELAN-TAG tag field comprises a 3-bit priority data field with a priority level of the telegram, the priority data field with the priority level being similar to the VLAN priority in a VLAN-TAG tag field. Using a 1-bit FragAllowed data field, a possible fragmentation or a fragmentability of the telegram is indicated to the receiving network subscriber  200 . The ELAN ID may be used to route the corresponding telegram in the automation network  100 , with the ELAN ID being e.g. located in an ELAN ID data field comprising 12 bits. The ELAN ID may be embodied in a similar manner to the VLAN ID, e.g. in the form of a hexadecimal number, as explained above. 
     Furthermore, the ELAN-TAG tag field has a 4-bit reserve data field for which no fixed assignment has yet been provided. An 8-bit FragOffset data field in the ELAN-TAG tag field is used to specify an offset of the data in the telegram, wherein the offset is calculated from the Ethertype data field of the telegram. Finally, the ELAN-TAG tag field further comprises a 16-bit FrameNo data field. The FrameNo data field comprises a number or a number of the telegram, which is incremented or incremented by the sender or by the person issuing the telegram in the automation network  100 . 
     Byte 20 in the telegram e.g. comprises an Ethertype data field. An EtherCAT telegram is identified by the value 0x88A4 (in hexadecimal system) in the Ethertype data field, because the EtherCAT protocol represents the used protocol of the next higher layer within the user data, i.e. within an Ethernet data section. A layer and a next higher layer are defined according to the OSI model. For comparison a telegram would have the value 0x0800 (in hexadecimal system) in the Ethertype data field, provided that the used protocol of the next higher layer within the user data forms the IP protocol (IP: Internet Protocol). 
     An Ethernet data section in the telegram may be embodied starting at byte 21, wherein the Ethernet data section in an EtherCAT telegram comprises an EtherCAT header and a plurality of EtherCAT datagrams. The EtherCAT header comprises an EtherCAT type data field with the value 1 or with the value 6, wherein a processing of the EtherCAT telegram is indicated by the value 1 of the EtherCAT type data field of a processor of a slave subscriber, whereas a blocking of the processing of the EtherCAT telegram is indicated by the value 6 of the EtherCAT type data field of the processor of a slave subscriber. 
     For example, the byte n may be in the form of the last byte of the Ethernet data section. Alternatively, the byte n may represent a padding data field, provided that via the EtherCAT telegram as user data e.g. less than 46 respectively 42 bytes (without respectively with a VLAN TAG according to the IEEE 802.1Q standard) are to be transmitted, wherein the preamble and the Start Frame Delimiter (SFD) data field are not counted. With the additional bytes added as pad which are inserted into the EtherCAT telegram, the Ethernet data telegram may be brought to the required minimum size of 64 bytes. 
     Alternatively, the byte n may be in the form of a padding length data field comprising a number or length of bytes appended as a pad. 
     If an ELAN-TAG tag field is located in the header section of a telegram, an end section of the telegram comprises a 1-byte ELAN-END-TAG data field ahead of a CRC data field that includes the value of a checksum. The ELAN-END-TAG data field has a 1-bit FragFollows data field, which is used to indicate whether at least one fragment of the fragmented telegram still follows. Furthermore, the ELAN-END-TAG data field comprises a 3-bit NextPrio data field that indicates the priority of the next telegram, provided that the priority of the following telegram is known. Finally, the ELAN-END-TAG data field may also comprise a 1-bit padding data field. Provided that the fragment of the telegram is the last fragment of the telegram and the last fragment includes bytes or padding bytes attached as pad, the bit of the padding data field is set and the byte n of the telegram has the number or the length of the padding bytes (padding length). The bytes (n+1) to (n+4) in the telegram indicate the CRC data field with the checksum of the telegram. 
     The automation network  100  comprising network subscribers  200  shown in the figures may also be implemented with more than two switches  210  and more than four network distributors. Similarly, the network distributors may each include more than three distribution ports. The additional distribution ports may either comprise the functionality of the first distribution ports and the third distribution ports of the network distributors, provided that further network distributors are connected to the additional distribution ports, or may comprise the functionality of the second distribution ports, to each of which only one slave subscriber  215  or a chain of slave subscribers  215  is connected. 
     Furthermore, the proposed method together with the proposed automation network  100  is not limited to telegram traffic in control mode, but may equally be used successfully during a configuration phase of the automation network  100  together with its network subscribers  200 , even in the event that a line interference occurs during the configuration phase of the automation network  100 . Thus, even for the configuration phase in which the further network subscribers  200  of the automation network  100  are e.g. first detected by the master subscriber  205 , continuous communication of the master subscriber  205  with the further network subscribers  200  to be detected may be guaranteed. 
     The invention has been described in detail using preferred embodiment examples. Instead of the described examples of embodiment, further examples of embodiment are conceivable, which may comprise further variations or combinations of described features. For this reason, the invention is not limited by the disclosed examples, since other variations may be derived therefrom by those skilled in the art without departing from the protective scope of the invention. 
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 List of reference numerals 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 100 automation network 
                 300 first double-ring structure 
               
               
                 200 network subscriber 
                 305 second double-ring structure 
               
               
                 205 master subscriber 
                 310 first master communication path 
               
               
                 210 switch 
                 315 second master communication path 
               
               
                 215 slave subscriber 
                 320 first slave communication path 
               
               
                 220 first telegram 
                 325 second slave communication path 
               
               
                 225 second telegram 
                 335 third slave communication path 
               
               
                 230 first network distributor 
                 340 fourth slave communication path 
               
               
                 235 second network distributor 
                 400 first master port 
               
               
                 240 first switch 
                 415 second master port 
               
               
                 245 second switch 
                 500 first switching port 
               
               
                 250 third network distributor 
                 515 second switching port 
               
               
                 255 fourth network distributor 
                 530 third switching port 
               
               
                 260 first slave subscriber 
                 550 fourth switching port 
               
               
                 262 second slave subscriber 
                 600 first slave port 
               
               
                 264 third slave subscriber 
                 620 second slave port 
               
               
                 266 fourth slave subscriber 
                 700 first distribution port of first network distributor 
               
               
                 268 fifth slave subscriber 
                 705 second distribution port of first network distributor 
               
               
                 270 sixth slave subscriber 
                 707 third distribution port of first network distributor 
               
               
                 272 seventh slave subscriber 
                 708 first distribution port of second network distributor 
               
               
                 274 eighth slave subscriber 
                 710 second distribution port of second network distributor 
               
               
                 276 ninth slave subscriber 
                 715 third distribution port of second network distributor 
               
               
                 278 tenth slave subscriber 
                 720 first distribution port of third network distributor 
               
               
                 280 eleventh slave subscriber 
                 725 second distribution port of third network distributor 
               
               
                 282 third telegram 
                 730 third distribution port of third network distributor 
               
               
                 284 fourth telegram 
                 735 first distribution port of fourth network distributor 
               
               
                 TX transmitter 
                 740 second distribution port of fourth network distributor 
               
               
                 RX receiver 
                 745 third distribution port of fourth network distributor 
               
               
                 X placeholder 
                 800 first internal connection