# US 10,484,138 B2 · Method for transmitting data packets on a data transmission path between two communication subscribers, automation system and computer program > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,484,138 B2 - Document ID: US10484138B2 - Status: Granted - Kind: B2 - Application number: 15/800,669 - Filed: 2017-11-01 - Published: 2018-05-03 - Granted: 2019-11-19 - Earliest claimed: 2016-11-03 - Assignees: Beckhoff Automation GmbH - Applicants: Beckhoff Automation GmbH - Inventors: Holger Büttner; Florian Essler; Rainer Hoffmann; Dirk Janssen; Karl Weber - Web page: https://patentgrep.com/patent/US10484138B2 ## CPC - H04L 1/08: by repeating transmission, e.g. Verdan system {(H04L1/1858 and H04L1/189 take precedence)} - H04L 1/1628: {List acknowledgements, i.e. the acknowledgement message consisting of a list of identifiers, e.g. of sequence numbers (H04L1/1614 takes precedence)} - H04L 1/1657: {Implicit acknowledgement of correct or incorrect reception, e.g. with a moving window} - H04L 1/1858: {Transmission or retransmission of more than one copy of acknowledgement message} - H04L 45/74: Address processing for routing - H04L 1/1874: {Buffer management} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A first communication subscriber transmits a first data packet comprising data and an identification character to the second communication subscriber. The first communication subscriber and the second communication subscriber respectively determine a first and a second acknowledgement character on the basis of the identification character. The second communication subscriber transmits a second data packet comprising the second acknowledgement character back to the first communication subscriber. The first communication subscriber can thus check, on the basis of the second acknowledgement character, whether the first data packet arrived at the second communication subscriber. ## Claims ### Claim 1 A method for transmitting data packets on a data transmission path between a first communication subscriber and a second communication subscriber, comprising the following steps of: transmitting a first data packet to the second communication subscriber by means of the first communication subscriber, the first data packet comprising at least data and an identification character, determining at least one first acknowledgement character on the basis of the identification character by means of the first communication subscriber, determining at least one second acknowledgement character on the basis of the identification character by means of the second communication subscriber if the second communication subscriber has received the first data packet, transmitting a second data packet comprising the second acknowledgement character to the first communication subscriber by means of the second communication subscriber, receiving the second data packet transmitted by the second communication subscriber by means of the first communication subscriber, checking, by means of the first communication subscriber, whether the received second acknowledgement character is correlated with the determined at least one first acknowledgement character in such a manner that it confirms the reception of the first data packet, and retransmitting the first data packet with the identification character to the second communication subscriber by means of the first communication subscriber if the received second acknowledgement character is not correlated with the determined at least one first acknowledgement character or the second acknowledgement character was not received by the first communication subscriber. ### Claim 2 (depends on 1) The method according to claim 1, the at least one first acknowledgement character and/or the at least one second acknowledgement character being a sequence of acknowledgement characters. ### Claim 3 (depends on 1) The method according to claim 1, a sequence of identifiers being used to determine the at least one first acknowledgement character and/or the at least one second acknowledgement character. ### Claim 4 (depends on 1) The method according to claim 1, the retransmission being carried out if a second or further data packet, the second acknowledgement character of which is not correlated with the determined at least one first acknowledgement character, is not received by means of the first communication subscriber within a predetermined time or if the second acknowledgement character was not received by the first communication subscriber within the predetermined time. ### Claim 5 (depends on 4) The method according to claim 4, the data packets being cyclically transmitted, the predetermined time corresponding to a predetermined number of cycles, with the result that the retransmission is carried out if a second or further data packet, the second acknowledgement character of which is not correlated with the determined at least one first acknowledgement character, is not received by means of the first communication subscriber within the predetermined number of cycles or if the second acknowledgement character was not received by the first communication subscriber within the predetermined number of cycles. ### Claim 6 (depends on 1) The method according to claim 1, the first communication subscriber comprising a plurality of buffers for storing data and a transmission buffer for storing data to be transmitted, data being read from one of the buffers and being written to the transmission buffer in order to transmit a data packet to the second communication subscriber, an identification character of a transmitted data packet indicating from which of the buffers the data in the transmitted data packet were read, with the result that the first acknowledgement character, on account of the dependence on the identification character, indicates from which of the buffers the data in the transmitted data packet were read, with the result that the received second acknowledgement character also indicates, on account of the correlation with the first acknowledgement character, from which of the buffers the data in the transmitted data packet were read, it being determined for retransmission which second acknowledgement character correlated with a first acknowledgement character has not been received, with the result that the first acknowledgement character associated with this second acknowledgement character is determined, with the result that the identification character associated with this first acknowledgement character is determined, the data being read from the buffer corresponding to the determined identification character and being written to the transmission buffer in order to retransmit these data to the second communication subscriber. ### Claim 7 (depends on 6) The method according to claim 6, the data in a buffer being released for overwriting only when the received second acknowledgement character is correlated with the determined first acknowledgement character or the second acknowledgement character has been received by the first communication subscriber. ### Claim 8 (depends on 1) The method according to claim 1, the second acknowledgement character being the same as the first identification character. ### Claim 9 (depends on 1) The method according to claim 1, an Ethernet-based field bus, in particular an EtherCAT field bus, being used as the data transmission path. ### Claim 10 An automation system comprising: a first communication subscriber and a second communication subscriber which are connected via a data transmission path and each have a connection unit for transmitting data packets on the data transmission path between the two communication subscribers, the connection unit of the first communication subscriber being configured to transmit a first data packet to the second communication subscriber, the first data packet comprising at least data and an identification character, the connection unit of the first communication subscriber being configured to determine at least one first acknowledgement character on the basis of the identification character, the connection unit of the second communication subscriber being configured to receive the first data packet and, if the first data packet is received, to determine at least one second acknowledgement character on the basis of the first acknowledgement character, and to transmit a second data packet comprising the second acknowledgement character to the first communication subscriber, the connection unit of the first communication subscriber being configured to receive a second data packet transmitted by the second communication subscriber and to check whether the received second acknowledgement character is correlated with the determined at least one first acknowledgement character in such a manner that it confirms the reception of the first data packet, and the connection unit of the first communication subscriber being configured to retransmit the first data packet with the identification character to the second communication subscriber if the received second acknowledgement character is not correlated with the determined at least one first acknowledgement character or the second acknowledgement character was not received by the first communication subscriber. ### Claim 11 (depends on 10) The automation system according to claim 10, the at least one first acknowledgement character and/or the at least one second acknowledgement character being a sequence of acknowledgement characters. ### Claim 12 (depends on 10) The automation system according to claim 10, a sequence of identifiers being used to determine the at least one first acknowledgement character and/or the at least one second acknowledgement character. ### Claim 13 (depends on 10) The automation system according to claim 10, the retransmission being carried out if a second or further data packet, the second acknowledgement character of which is not correlated with the determined at least one first acknowledgement character, is not received by means of the first communication subscriber within a predetermined time or if the second acknowledgement character was not received by the first communication subscriber within the predetermined time. ### Claim 14 (depends on 13) The automation system according to claim 13, the data packets being cyclically transmitted, the predetermined time corresponding to a predetermined number of cycles, with the result that the retransmission is carried out if a second or further data packet, the second acknowledgement character of which is not correlated with the determined at least one first acknowledgement character, is not received by means of the first communication subscriber within the predetermined number of cycles or if the second acknowledgement character was not received by the first communication subscriber within the predetermined number of cycles. ### Claim 15 (depends on 10) The automation system according to claim 10, the first communication subscriber comprising a plurality of buffers for storing data and a transmission buffer for storing data to be transmitted, data being read from one of the buffers and being written to the transmission buffer in order to transmit a data packet to the second communication subscriber, an identification character of a transmitted data packet indicating from which of the buffers the data in the transmitted data packet were read, with the result that the first acknowledgement character, on account of the dependence on the identification character, indicates from which of the buffers the data in the transmitted data packet were read, with the result that the received second acknowledgement character also indicates, on account of the correlation with the first acknowledgement character, from which of the buffers the data in the transmitted data packet were read, it being determined for retransmission which second acknowledgement character correlated with a first acknowledgement character has not been received, with the result that the first acknowledgement character associated with this second acknowledgement character is determined, with the result that the identification character associated with this first acknowledgement character is determined, the data being read from the buffer corresponding to the determined identification character and being written to the transmission buffer in order to retransmit these data to the second communication subscriber. ### Claim 16 (depends on 15) The automation system according to claim 15, the data in a buffer being released for overwriting only when the received second acknowledgement character is correlated with the determined first acknowledgement character or the second acknowledgement character has been received by the first communication subscriber. ### Claim 17 (depends on 10) The automation system according to claim 10, the second acknowledgement character being the same as the first identification character. ### Claim 18 (depends on 10) The automation system according to claim 10, an Ethernet-based field bus, in particular an EtherCAT field bus, being used as the data transmission path.