Synchronous data network system and method for initializing and synchronizing same

Abstract

The invention relates to a synchronous data network system (10) comprising: a data network (100) connecting data network nodes (110) to each other for exchanging data via a direct bidirectional data transmission link (x) between adjacent data network nodes (110); any node chain of data network nodes (110), the node chain consisting of a first data network node (110A), a second data network node (110B) and a third data network node (110C) consecutive, the second data network node (110B) is designed to receive, on a data forwarding link (xABBC), data transmitted from the first data network node (110A) on a first direct data transmission link (xAB) between the first data network node (110A) and the second data network node (110B), and is designed to forward the data to the third data network node (110C) in transmission mode on a second direct data transmission link (xBC) between the second data network node (110B) and the third data network node (110C). The synchronous data network system (10) is characterized in that the second data network node (110B) is designed to delay the forwarding of data on the single-hop data forwarding link (xABB, xBBC) between the first data network node (110A) and the third data network node (110C) such that the hop delay (dHABB, dHBBC) equals a predetermined fixed common hop delay (dCH). Thus, this results in a simple method for implementing implicit time synchronization of a data network system.

Description

[0001] The present invention relates to a synchronized data network system, in particular a data network system for use as an avionics system data network for deterministic and potentially flight safety-related communication between data network participants. Furthermore, the present invention relates to a method for initializing and synchronizing a data network system.

[0002] When using data network components in avionics systems, it is often necessary to achieve or facilitate deterministic communication between participants in the avionics system data network. This is often a stringent requirement, for example, where communication is an essential part of functionality that has a direct or indirect impact on flight safety. Determinism is an abstract term and is described in document DO-297, "Integrated Modular Avionics (IMA) Development Guidance and Certification Considerations," dated November 8, 2005, RTCASC-200, EUROCAE WG-6, as the ability to produce predictable results based on previous operations, where the results are repeatable within a specified time window.

[0003] One approach on how to achieve deterministic behavior enforcement for data networks is by having absolute control over network data traffic in time and space, which allows providing bandwidth guarantees for communications between any two participants in the network during precisely defined time periods.

[0004] A fundamental part of achieving this is ensuring that each data network node in the data network system (which is connected to other data network nodes via the data network through corresponding direct data transmission links) has a common understanding of the current system time with a minimum acceptable deviation in accuracy. Therefore, in order for a deterministic data network system to function, it is necessary that all components or data network nodes included in the data network are synchronized with each other and have a common time base. This common clock time can be achieved through various time synchronization tools, such as the Precision Time Protocol (PTP) and its corresponding enhancements for modern time-sensitive networks. Industry-standard methods.

[0005] Industry-standard methods for time synchronization (hereafter referred to as synchronization) are optimized for use in complex, dynamically changing, open networks and require complex methods to establish a common time base among all participants. In contrast, avionics network systems are typically pre-fabricated and closed systems to limit complexity. Therefore, in these situations, efficient methods with more streamlined means for synchronization and verification of deterministic behavior are needed.

[0006] Compared to avionics system data network standards known in the art (such as ARINC-664, Part 7, AFDX) or standards still under development (such as CAIN for TSN), it is necessary to implement significantly lower complexity of network components to reduce costs, simplify network computing power for synchronization, reduce the time required to achieve safety certification, and achieve increased efficiency.

[0007] The present invention is therefore based on the object of providing a synchronous data network system and a method for initializing and synchronizing the same, by means of which system a lower complexity of network components, a reduction in costs, a significant simplification of the computing power required for synchronization, a reduction in the time required for security authentication and an increase in efficiency can be achieved.

[0008] This object is achieved by a synchronous data network system according to claim 1 and a method according to claims 13 and 14. Advantageous embodiments and further developments of the invention are set forth in the dependent claims.

[0009] According to the present invention, a synchronous data network system is provided, comprising a data network that connects data network nodes to each other via direct data transmission links between adjacent data network nodes for data exchange. According to the present invention, a node chain consisting of a first data network node, a second data network node, and a third data network node is provided among these data network nodes, wherein the second data network node is adapted to receive data transmitted on a first direct data transmission link between the first and second data network nodes from the first data network node on a data forwarding link, and is adapted to forward the data to the third data network node in a transmission mode on a second direct data transmission link between the second and third data network nodes. In this process, the second data network node is adapted to delay the forwarding of data on the single-hop data forwarding link between the first and third data network nodes so that the hop delay is equal to a predetermined fixed common hop delay.

[0010] Therefore, a synchronous data network system is provided, in which the data network nodes participating in the network are designed so that when data from a transmitting data network node is forwarded to a receiving data network node, the inserted forwarding data network node delays the forwarding of the data so that the hop period or hop delay no longer depends on the network-specific or node-specific delay, but is equivalent or balanced for each forwarding node to a fixed hop delay that is equal and common to all nodes.

[0011] Although this delay slightly increases the response time or transmission latency, the data throughput remains unchanged and at the same time the synchronization of the entire network is greatly simplified. This is because, by amplifying the timestamp of the synchronization packet transmitted by the master node by multiplying the number of hops by a fixed common hop delay when the synchronization data packet from the master data network node (usually an ordinary data packet with corresponding header information) arrives at the slave data network node, the synchronization data packet can be used to synchronize the slave clock of the slave data network node with the master clock in the simplest possible way.

[0012] The synchronization of the data network system described below can also be used in decentralized data networks if several network components have a reliable master clock. The present invention thus provides a highly redundant method for synchronizing a data network system for deterministic communication between network participants.

[0013] In case of implicit synchronization of a data network system by means of a master data network node having a master clock, the master data network node will have a master clock timestamp t tx The synchronization data packet is transmitted to the slave data network node, and the number of hops h of the synchronization data packet completed between the master data network node and the corresponding slave data network node and the common hop delay period d are calculated. CH , based on the formula t master =t tx +d CH *h. It is preferred to synchronize the slave clocks of the slave data network nodes with the master clock.

[0014] There are two ways to define a single-hop data forwarding link for balancing common hop delays via the single-hop data forwarding link. On the one hand, for example, the single-hop data forwarding link can correspond to a data forwarding link that starts on the transmitting side of a first data network node, passes through the second data network node via a direct data transmission link between the first data network node and the second data network node, and ends on the transmitting side of the second data network node. On the other hand, the single-hop data forwarding link can also be defined so that the single-hop data forwarding link corresponds to a data forwarding link that starts on the receiving side of the second data network node, passes through the second data network node, and ends on the receiving side of the third data network node via a direct data transmission link between the second data network node and a third data network node.

[0015] For the practical implementation of the synchronous data network system, it is advantageous if the second data network node includes: a data transmission unit, which is connected to the direct data transmission link for transmitting data to other data network nodes; a data receiving unit, which is connected to the direct data transmission link for receiving data from other data network nodes; a delay matching unit, which is suitable for calculating the delay matching period specific to the current single-hop data forwarding link with the help of the stored specific hop delay of the current single-hop data forwarding link and with the help of a predetermined fixed common hop delay period; and a delay buffer, which is inserted between the data receiving unit and the data transmission unit so that the forwarding of the data packet on the current single-hop data forwarding link is delayed by the specific delay matching period received from the delay matching unit.

[0016] In this process, it is useful if the delay matching unit comprises: a timer for measuring the round trip delay on the single-hop data forwarding link to be measured; a memory for storing the inherent node delay, the round trip delay of the single-hop data forwarding link of the second data network node, and a predetermined fixed common hop delay; and a calculation unit adapted to calculate the delay matching unit using the formula d ARX =d CH -d RT / 2-d SRX_B To calculate the delay matching period.

[0017] For the practical implementation of the initialization and synchronization of the data network system of the invention, it is advantageous if the second data network node comprises: a communication control unit for controlling the initialization and synchronization; an initialization control unit which controls the initialization process of the data network node; and a synchronization control unit which controls the synchronization of the data network node.

[0018] In this process, it is useful if the initialization control unit prompts the second data network node, which is a slave data network node, to perform the following steps: transmitting a round-trip measurement command from the communication control unit to the data transmission unit; transmitting a round-trip signal or ping signal by the data transmission unit to the data receiving unit of the corresponding receiving data network node via the corresponding direct data transmission link of the single-hop data forwarding link to be measured; starting a timer by the delay matching unit when transmitting the round-trip signal; receiving the round-trip signal sent back from the corresponding data network node via the corresponding direct data transmission link by the data receiving unit; stopping the timer by the delay matching unit when receiving the round-trip signal sent back; reading the round-trip delay from the timer; calculating the specific hop delay of the single-hop data forwarding link to be measured by adding the inherent node delay to half of the round-trip delay; repeating these steps for all single-hop data forwarding links to be measured; and storing the explicit hop delays of all single-hop data forwarding links to be measured.

[0019] Optionally, if the common hop delay of all explicit hop delays from all single-hop data forwarding links to be measured is determined by the master data network node during initialization, an additional step of transmitting the explicit hop delays of all single-hop data forwarding links to be measured to the master data network node can be performed.

[0020] If the second data network node acts as a master data network node, it is advantageous when the initialization control unit prompts the second data network node, acting as a slave data network node, to perform the following steps: receiving from the slave data network node the respective explicit hop delays of all single-hop data forwarding links of the slave data network nodes to be measured; and specifying a common hop delay based on the transmitted hop delays, wherein the predetermined fixed common hop delay is greater than all transmitted hop delays.

[0021] To ensure that the chosen fixed common hop delay is not unnecessarily large, it is useful if the fixed common hop delay corresponds to a time period that is equal to the longest time period of the hop delay scaled with a safety factor greater than 1 or with a safety bias.

[0022] When the data network system is synchronized by a second data network node acting as a slave data network node, it is advantageous when the synchronization control unit prompts the second data network node acting as a slave data network node to perform the following steps: receiving a time stamp t from the master data network node having the master clock tx and according to the synchronization data packet between the primary data network node and the second data network node to complete the hop number h and by means of a common deterministic hop delay period d CH , based on the formula t master =t tx +d CH *h. Synchronize the slave clock of the second data network node with the master clock time.

[0023] If the second data network node acts as the master data network node, then when the synchronization control unit prompts the second data network node, which is the master data network node, to tx The master clock timestamp t is transmitted to the slave data network node tx It is beneficial when synchronizing packets.

[0024] In order to make the hop count and the master clock timestamp available to the slave data network node in a simple manner and to ensure that synchronization occurs due to authorized synchronization of the data packets of the master node, it is very advantageous if the synchronization data packet also includes the hop count and an identifier of the master data network node in addition to the master clock timestamp.

[0025] The synchronous data network system according to the present invention offers significant advantages over the prior art when used as an avionics system data network for deterministic and / or flight safety-related communication between data network nodes. This is particularly useful when the data network has a ring, star, or bidirectional data exchange structure.

[0026] In addition, according to the present invention, a method for initializing the synchronous data network system of the present invention is provided, which method includes the following steps: transmitting a round-trip measurement command from a communication control unit of a slave data network node to a data transmission unit of the slave data network node; transmitting a round-trip signal or a ping signal by the data transmission unit of the slave data network node to a data receiving unit of a corresponding additional slave data network node via a corresponding direct data transmission link of a single-hop data forwarding link to be measured; starting a timer of the slave data network node by a delay matching unit of the slave data network node when transmitting the round-trip signal; receiving a round-trip signal sent back from the corresponding additional slave data network node via a corresponding direct data transmission link by the data receiving unit of the slave data network node; stopping the timer by the delay matching unit of the slave data network node when receiving the round-trip signal sent back; reading the round-trip delay from the timer of the slave data network node; calculating the specific hop delay of the single-hop data forwarding link to be measured by adding the inherent node delay to half of the round-trip delay; repeating these steps for all single-hop data forwarding links to be measured; and storing the explicit hop delays of all single-hop data forwarding links to be measured.

[0027] Optionally, if a common hop delay of all explicit hop delays from all single-hop data forwarding links to be measured is determined by the master data network node during initialization, the following additional steps may be performed: the explicit hop delays of all single-hop data forwarding links to be measured are transmitted to the master data network node; the master data network node receives the corresponding explicit hop delays of all single-hop data forwarding links of the slave data network nodes to be measured; and the master data network node specifies a common hop delay based on the transmitted hop delays, wherein the predetermined fixed common hop delay is greater than all transmitted hop delays.

[0028] Furthermore, according to the present invention, there is provided a method for synchronizing a synchronous data network system of the present invention comprising at least one master data network node and a slave data network node, the method comprising the steps of: synchronizing the master data network node at a time t tx The master clock timestamp t is transmitted to the slave data network node tx Synchronous data packet; received from the data network node with the master clock from the master data network node with the master clock timestamp t tx The synchronization data packet and the number of hops h of the synchronization data packet between the master data network node and the slave data network node and the common deterministic hop delay dCH , based on the formula t master =t tx +d CH *h, synchronizes the slave clock of the slave data network node with the master clock time.

[0029] According to the present invention, there are also provided a synchronous data network system, a master data network node and a slave data network node, each of which is adapted to perform the above-mentioned method according to the present invention.

[0030] The present invention will be described in more detail below by way of examples based on the accompanying drawings.

[0031] Figure 1 shows a highly simplified schematic diagram of a synchronous data network system in a ring structure according to the present invention,

[0032] Figure 2 showing a node chain of a first data network node, a second data network node and a third data network node connected to each other via a first direct data transmission link and a second direct data transmission link,

[0033] Figure 3A shows a time flow diagram of the delay in forwarding data through the second data network node according to a first exemplary embodiment of the present invention,

[0034] Figure 3B shows a time flow diagram of the delay of data passing through the second data network node according to a second exemplary embodiment of the present invention,

[0035] Figure 4A shows a node chain of a first data network node, a second data network node, a third data network node and a fourth data network node according to a first exemplary embodiment of the present invention, illustrating delays in data forwarding for synchronization purposes,

[0036] Figure 4B shows a node chain of a second data network node, a third data network node, a fourth data network node and a fifth data network node according to a second exemplary embodiment of the present invention, illustrating the time flow of delays in data forwarding for synchronization purposes,

[0037] Figure 5 shows a highly simplified schematic block diagram of a data network node according to the invention,

[0038] Figure 6A and Figure 6B shows the components of a data network node according to the invention and their role in initializing a synchronous data network system,

[0039] Figure 7A process flow chart showing a method for initializing a synchronous data network system according to the present invention is shown, and

[0040] Figure 8 A process flow chart of a method for synchronizing a synchronous data network system according to the present invention is shown.

[0041] In the various figures of the drawings, components that correspond to each other are provided with the same reference numerals.

[0042] Figure 1 An exemplary embodiment of a synchronous data network system 10 according to the present invention is shown. The synchronous data network system 10 comprises a data network 100 which connects data network nodes 110 to each other for data exchange purposes via direct data transmission links x between adjacent data network nodes 110. Figure 1 In the depicted exemplary embodiment of the present invention, data network nodes 110A, 110B, 110C and 110D transmit data via direct data transmission links x AB 、x BC 、x CD 、x AD connected to each other in a ring structure. Figure 1 The data network system 10 in the embodiment has a ring structure, but a data network 100 having a star or mesh structure can also be provided as the data network system 10. The present invention can be applied to any network topology and is therefore not limited to a specific network structure. Therefore, the topology of the network structure is free; the only requirements are the bidirectionality of the connections between the nodes and that at least one node must have more than one interface to a neighboring node to enable the generation of a topology with more than two participants. The number of data network nodes 110 is also arbitrary; Figure 1 The four data network nodes 110A, 110B, 110C and 110D depicted in FIG. 1 are to be understood as purely examples.

[0043] Prefabricated avionics components are preferably provided as data network nodes 110 in the data network system 10 to provide an avionics system data network, via which deterministic and potentially flight-safety-relevant communication can take place between the avionics components serving as data network nodes. This deterministic communication is particularly necessary in flight networks or when using autonomous flight or piloting applications, as synchronized communication and traceability of causal chains within the avionics systems are required, particularly for demonstrating flight safety, but also for flight safety itself. These systems are used when protecting human life, completing military missions, or transporting high-value assets are at risk. Avionics components used as data network nodes 110 within the meaning of the present invention include various avionics components, such as computer systems for flight control or mission management, human-machine interfaces such as displays or input devices, flight attitude sensors, engine sensors and actuators, tail sensors and actuators, or weapon systems (in which weapons can be triggered or decoys can be launched via a synchronized data network system). Although use in avionics is particularly preferred, the use of the synchronous data network system according to the invention is not limited thereto but can, for example, be used in the fields of navigation, aerospace (such as in satellite systems) or in large safety-related plants.

[0044] In the data network system 10 according to the present invention, the direct data transmission link x between two data network nodes 110 can realize bidirectional or dual simplex communication. The time behavior of data sent through the network 100 is mainly determined by the one-way hop delay d H and the combined round trip delay d RT To characterize it, for each link it depends on external factors such as the physical medium or environmental conditions as well as internal factors such as the design or implementation of the data network node 110 .

[0045] Due to the hop delay d on the data network system 10 H The runtime for transmitting a data packet from a source data network node 110 to an end recipient data network node 110 is not a direct function of the data forwarding link selected by the data network 100 and the number of hops on that data forwarding link. Instead, all specific delays caused by factors external or internal to the network need to be taken into account, which means a huge computational effort when one wants to implicitly synchronize the data network system 10. In this case, implicit synchronization means that the data network system 10 is synchronized by the master data network node 110M ( Figure 5 ) transmits synchronization data packets to the data network node 110 to synchronize the slave clocks of all network nodes to the master clock of the master data network node 110M.

[0046] Furthermore, such synchronization is not only computationally intensive but also depends on runtime initialization and thus also has an impact on the determinism of the system, since tolerances over the entire runtime-relevant value range are required.

[0047] exist Figure 2 In FIG. 1 , a synchronous data network system 10 according to the present invention is depicted in more detail, wherein various delays generated by the data network nodes 110 or by the direct data transmission link x are discussed in more detail here. Figure 2 1 shows a node chain of data network nodes 110 according to the present invention, which consists of a first network node 110A, a second network node 110B and a third data network node 110C in succession, which data network nodes transmit data via a direct data transmission link xA during data transmission from the data network node 110A to the data network node 110C. B and x BC connected to each other via direct transmission link x CB and x BA ,Bidirectional communication is also possible, however, for simplicity reasons, only the forwarding direction from node 110A to 110C is considered.

[0048] According to the present invention, the second data network node 110B is adapted to connect the data forwarding link x ABBC A first direct data transmission link x between the first data network node 110A and the second data network node 110B is received from the first data network node 110A. AB and a second direct data transmission link x between the second data network node 110B and the third data network node 110C. BC The data is forwarded to the third data network node 110C.

[0049] Therefore, according to the present invention, the direct data transmission link x as part of the data network 100 is combined with the data forwarding link x ABBC To distinguish, data forwarding link x ABBC Also included are transmission links through data network nodes 110 having corresponding inherent node delays.

[0050] In particular, the single-hop data forwarding link x AAB 、x ABB 、x BBC 、x BCC or often referred to as x in the following text XZZ or x ZZY is of interest to the present invention because it is the smallest unit of data forwarding hop from one data network node 110 to another data network node 110. There are two possible ways to define a single-hop data forwarding link:

[0051] (a) A single-hop data forwarding link can be defined so that it corresponds to the data forwarding link x ABB and x BCC Therefore, the direct data transmission link x from the transmitting data network node 110A to the forwarding data network node 110B AB and the data forwarding link through the data network node 110B are combined into a single-hop data forwarding link in this case. In the case where the data network node 110C is the forwarding data network node 110, the direct data transmission link x BC and the data forwarding links passing through the data network node 110C are combined into a single-hop data forwarding link x BCC Therefore, in the case where the second data network node 110B is the forwarding data network node 110, the single-hop data forwarding link corresponds to the data forwarding link x ABB , the data forwarding link x ABB Starting at the transmitter side of the first data network node 110A, a direct data transmission link x is transmitted between the first data network node 110A and the second data network node 110B. AB It passes through the second data network node 110B and ends at the transmitter side of the second data network node 110B.

[0052] (b) According to the second exemplary embodiment, a single-hop data forwarding link x AAB 、x BBC The forwarding link with the corresponding delay of the forwarding node 110 and the subsequent direct data transmission link x AB 、x BC Composed, via these direct data transmission links x AB 、x BC , data originating from the forwarding data network nodes 110A, 110B are transmitted to the respective additional data network nodes 110B, 110C. This therefore means that in the case where the second data network node 110B is the data forwarding data network node, the single-hop data forwarding link corresponds to the data forwarding link x BBC , the data forwarding link x BBC Starting at the receiver side of the second data network node 110B, passing through the second data network node 110B, via a direct data transmission link x between the second data network node 110B and the third data network node 110C BC , and ends at the receiver side of the third data network node 110C.

[0053] As in Figure 2As can be further seen in FIG, corresponding delays are assigned to the corresponding forwarding links through the data network node 110 and through the direct data transmission link x, which delays are related to the running time or delay d when the data is forwarded through the data network node 110. SRX_A d SRX_ B、d SRX_C Related to, or related to when data passes through a network with a delay d AB and d BC Direct data transmission link x AB and x BC It is related to the runtime or latency during forwarding.

[0054] Regarding the single-hop data forwarding link, the inherent node delay d SRX The sum of the transmission delay via the direct data forwarding link x is the hop delay d H_AAB d H_ABB d H_BBC and d H_BCC .although Figure 2 The hop delays in are all depicted as being of the same magnitude, but the following problem with the known data network system 10 immediately arises: variations in the inherent node delays and transmission delays make implicit synchronization of the data network system 10 very complex.

[0055] However, according to e.g. Figure 3A and Figure 3B The illustrated synchronous data network system 10 of the present invention overcomes this problem. Figure 3A Shown according to Figure 2 Detailed view of the embodiment in which a delay in data forwarding according to the first exemplary embodiment occurs, Figure 3B Depicted in Figure 2 The portion represents a delay in data forwarding according to the second exemplary embodiment of the present invention.

[0056] like Figure 3A As depicted, the second data network node 110B is adapted to enable a single-hop data forwarding link x between the first data network node 110A and the third data network node 110C. ABB The data forwarding delay on the hop delay d H_ABB Equal to the predetermined fixed common hop delay d CH In this process, the single-hop data forwarding link corresponds to the data forwarding link x ABB , the data forwarding link x ABB Starting at the transmitter side of the first data network node 110A, a direct data transmission link x is transmitted between the first data network node 110A and the second data network node 110B. AB It passes through the second data network node 110B and ends at the transmitter side of the second data network node 110B.

[0057] exist Figure 3B In the embodiment, the second data network node 110B is adapted to enable a single-hop data forwarding link x between the first data network node 110A and the third data network node 110C. BBC The data forwarding delay on the hop delay d H_BBC Equal to the predetermined fixed common hop delay d CH In this process, the single-hop data forwarding link corresponds to the data forwarding link x BBC , the data forwarding link x BBC Starting at the receiver side of the second data network node 110B, passing through the second data network node 110B, via a direct data transmission link x between the second data network node 110B and the third data network node 110C BC , and ends at the receiver side of the third data network node 110C.

[0058] Even though exemplary embodiment (a) is discussed for the sake of completeness ( Figure 3A ) and (b)( Figure 3B ) both, but the first exemplary embodiment (a) is preferred because the practical implementation of the second exemplary embodiment (b) is somewhat more difficult. In particular, Figure 3B In a second exemplary embodiment, an outgoing locally generated packet must be generated in the RX path of the second data network node 110B, the packet must be time-stamped and the transmission link TX towards the second data network node 110B is delayed. This also makes any data transfer delays between adjacent nodes 110 unnecessary (see also Figure 5 The paths in IDP->RDP_loc and IDP->RDP_fwd_AC).

[0059] According to the present invention, the intrinsic node delay d SRX_B Therefore, by means of the delay circuit in the forwarding data network node 110, the variable node delay d AX ABB or d AX BBC Extension, so that regardless of the data transmission link delay d AB or d BC Regardless of the inherent node delay d in the forwarding hop through the second data network node 110B SRX_B How, forwarding runtime or forwarding delay or single-hop data forwarding delay d H_ABB or d H_BBC Always equal to the predetermined common hop delay d CHThis is true regardless of which data network node 110 is selected in the synchronous data network system 10 according to the present invention or which associated direct data transmission link x of the selected single-hop data forwarding link is selected.

[0060] Although according to the present invention, the delay circuits in the second network node 110B and all other forwarding data network nodes 110 delay the data transmission in the data network system 10, this approach greatly simplifies the synchronization of the entire data network system 10. For the first exemplary embodiment of the present invention, this Figure 4A and for the second exemplary embodiment of the present invention, this is illustrated in Figure 4B Example in.

[0061] Thus, the synchronization of the data network system 10 according to the present invention can be achieved, for example, by using the master data network node 110M ( Figure 5 ) so that the corresponding slave data network node 110S of the data network system 10 is aligned with the master clock CLK_M ( Figure 5 For this purpose, the master data network node 110M is adapted to transmit data with a master clock timestamp t to the slave data network node 110S at periodic intervals or according to the user's instructions. tx The synchronization data packet SDP and the number of hops h of the synchronization data packet SDP completed between the master data network node 110M and the corresponding slave data network node 110S and the common hop delay period d CH , based on the formula t master =t tx +d CH *h, synchronizes the slave clock CLK_S of the slave data network node 110S with the master clock of the master data network node 110M.

[0062] Through the following Figure 4A and Figure 4B The synchronization using the above simple formula is made possible by the fact that, from the data network node 110A to 110D ( Figure 4A ) or from data network node 110B to 110E ( Figure 4B The forwarding of the synchronization data packet SDP has a well-defined time period from the master data network node 110M to the slave data network node 110S to be synchronized, i.e. the number of hops from the master data network node 110M to the respective slave data network node 110S multiplied by a predetermined fixed common hop delay d CH . Data transmission link x AB 、x BC 、x CD 、x DEcan be of various natures, wherein, in addition to wired or cable connections or fiber optic connections, for example, cable-free or wireless radio connections for direct data transmission links x are also possible. In addition, the intrinsic node delay d SRX It can also be different because, regardless of the selection of the data network node 110, during data forwarding, the hop delay is always adjusted or equalized to a predetermined common fixed hop delay d CH .

[0063] It is emphasized that, while synchronization of data network system 10 according to the present invention is preferred by means of master data network node 110M, synchronization can also occur in a decentralized data network system if several network nodes are equipped with clocks suitable for use as master clocks. For example, it is also conceivable that not only one master data network node 110M is provided, but that multiple data network nodes 110, or even all data network nodes 110, can operate as master data network nodes 110M, thereby maximizing the fail-safety and redundancy of synchronized data network system 10 according to the present invention. In this case, appropriate coordination between data network nodes 110 is merely required so that no two data network nodes 110 simultaneously assume the master role.

[0064] With the synchronization method according to the invention, synchronization of all data network nodes can be achieved in a simple manner with the aid of a hop delay which is identical for all data network nodes and corresponding forwarding links and common to all connections in a closed network.

[0065] exist Figure 5 , a block diagram of a data network node 110 according to the present invention is depicted. In this case, for example, the second data network node 110B comprises a data transmission unit TX, which is connected to the direct data transmission link x for transmitting data ODP to other data network nodes 110, the data ODP being a locally generated data packet TDP_loc to be transmitted or a forwarded data packet RDP_fwd to be transmitted. The second data network node 110B further comprises a data reception unit RX, which is connected to the direct data transmission link x for receiving data IDP from other data network nodes 110. Figure 5 As depicted, the second data network node 110B further comprises a delay matching unit LMU adapted to use the stored current single-hop data forwarding link x ABB 、x BBC The specific hop delay d H_ABB d H_BBC And by means of a predetermined fixed common hopping delay period d CH To calculate the specific current single-hop data forwarding link x ABB 、x BBCDelay matching period d ARX In the case of forwarding the data packet IDP from the data receiving unit RX to the other data network node 110 via the data transmission unit TX, the data packet RDP_fwd (for example, RDP_fwd_AC or RDP_fwd_CA) passes through the delay buffer CDB inserted between the data receiving unit RX and the data transmission unit TX designated for forwarding, so that the data packet RDP_fwd_AC is transmitted on the current single-hop data forwarding link x ABB 、x BBC The forwarding on the data delay matching unit LMU receives a specific delay matching period d ARX Delay.

[0066] exist Figure 6A The structure of the delay matching unit LMU is depicted in FIG. The LMU has a function for measuring the single-hop data forwarding link x ABB 、x BBC The round trip delay d RT The timer for measuring and storing the inherent node delay d SRX_B , single-hop data forwarding link x of the second data network node 110B ABB 、x BBC The round trip delay d RT and the predetermined fixed common hop delay d CH Furthermore, the delay matching unit LMU has a calculation unit adapted to use the formula d ARX =d CH -d RT / 2-d SRX_B To calculate the delay matching period d specific to the single-hop data forwarding link ARX_ABB .

[0067] like Figure 5 As depicted, data packets are delayed only when they are destined for forwarding, while received data packets RDP_loc that are not synchronization packets and are destined for local further processing in the corresponding second data network node 110B are not delayed. Thus, according to the first exemplary embodiment, a configurable delay in data forwarding is preferably provided on the receiver side of the respective node, specifically for packets that have not yet reached their destination address and are being forwarded to the data transmission unit TX for forwarding from the data receiving unit to the data transmission unit. In this way, in contrast to the implementation according to the second exemplary embodiment of the present invention, in which delays occur on the transmitting side of the forwarding link to be covered by the next data network node 110, locally further processed packets can be sent quickly and directly to the end user without further delay.

[0068] like Figure 5As further depicted in FIG, second data network node 110B has either a master clock CLK_M or a slave clock CLK_S, depending on whether second data network node 110B operates as master data network node 110M or slave data network node 110S. When second data network node 110B operates as slave data network node 110S, slave clock CLK_S is synchronized with master clock CLK_M of another master data network node 110M via a synchronization data packet SDP, which is received without delay according to the second exemplary embodiment or after delay by a delay buffer CDB according to the first exemplary embodiment. Second data network node 110B also includes a communication control unit LCU / CONFIG for controlling initialization and synchronization. Communication control unit LCU / CONFIG includes an initialization control unit LCU for controlling the initialization process of data network node 110 and a synchronization control unit CONFIG for controlling synchronization of data network node 110.

[0069] In the following text, an initialization process of a synchronous data network system according to the present invention and a subsequent synchronization process of the data network 10 according to the present invention will be described.

[0070] During network initialization, all nodes in the network are prompted to independently determine the delays on all data transmission links to their neighboring nodes in the network. In this process, the data network node interface implementation must be symmetrical or have known asymmetries that are taken into account by the neighboring nodes. Therefore, the hop delay can be correctly derived from the round-trip delay measurement. Then, before completing the network initialization, each individual node is prompted to add a delay or a specific delay matching period d ARX inserted into the data receive paths associated with all data transmission links and connections to neighboring nodes so that the resulting hop delay on all these connection links corresponds to a configurable common value for the entire network, which is determined before the network is enabled based on all single-hop data forwarding delays. This value is a predetermined fixed common hop delay d CH or common deterministic hop delay d CH .

[0071] At this point, it should be emphasized that the initialization of the network is completely decentralized and the distinction between slave data network nodes 110S and master data network nodes 110M is initially irrelevant, since the master data network node 110M, which is a successor to the slave data network node 110S, initially also undergoes the same initialization process as all other data network nodes 110. This means that as part of the network initialization (generating requests, receiving responses, and receiving requests and generating responses), all nodes determine the round-trip delays to their neighbors. There are no roles here, and all nodes are equal. Once the necessary information has been determined by each node, the target delay is set and the initialization phase ends. The uniform hop delays then achieve implicit time synchronization, simply because the defined master node regularly communicates with all other nodes (unidirectionally, no response required).

[0072] In detail, from the perspective of the second data network node 110B which plays the role of the slave data network node 110S, initialization is performed by an exemplary detection of a single-hop data forwarding link to its neighboring node 110A as follows: Figure 6A and Figure 6B shown.

[0073] Therefore, during the initialization process of the synchronous data network system 10, the initialization control unit LCU prompts the second data network node 110B, which is the slave data network node 110S, to perform the following steps. First, the slave communication control unit LCU sends a round trip measurement request RTMR to the data transmission unit TX. Then, in the case of the implementation of the first exemplary embodiment of the present invention, the data transmission unit TX transmits a round trip measurement request RTMR via the exemplary single-hop data forwarding link x to be measured. ABB The corresponding direct data transmission link x (in this case x AB ), transmits a round-trip signal or ping signal to the data receiving unit RX of the corresponding receiving data network node 110A. When the round-trip signal is transmitted, the timer of the delay matching unit LMU is synchronously started by the delay matching unit LMU. The round-trip signal or ping signal transmitted to the data network node 110A is received by the data receiving unit RX of the data network node 110A and a measurement request response MRR ( Figure 6B ) is sent back again directly to the receiving unit RX of the second data network node 110B. Once the data receiving unit RX has received the data via the corresponding direct data transmission link x AB The timer is stopped by the delay matching unit LMU upon receiving the round-trip signal sent back from the corresponding first data network node 110A.

[0074] The round trip delay d is read from the timer of the delay matching unit LMU. RTAfterwards, the delay matching unit LMU is calculated by transforming the inherent node delay d SRX_B Add the round-trip delay d RT half of the Figure 6A and Figure 6B In the example, the single-hop data forwarding link x to be measured ABB The specific hop delay d H_ABB The second data network node 110B can determine the intrinsic node delay d by internally measuring the internal forwarding delay of the data packet from the data receiving unit RX to the data transmission unit TX. SRX_B The intrinsic node delay value may also be measured when establishing a participating data network node and stored or saved in a memory of the delay matching unit LMU.

[0075] Since the second data network node 110B must measure any and all single-hop data forwarding links x according to the first or second exemplary embodiment XBB 、x BBY To complete the initialization of the data network system 10 , the above initialization process is repeated until the second data network node 110B has measured any and all single-hop data forwarding links to its directly connected data network nodes 110 .

[0076] If a “worst case” hop delay has been identified during the validation phase of the platform, then as a configuration this hop delay is a predefined common hop delay d known to each data network node 110. CH .

[0077] However, the network itself can also dynamically determine the common hop delay d CH , in order to optimize the total latency. In this case, this can be done, for example, via the master data network node 110M, but it is also possible to use an external reader that is connected to the network once during initialization to read out all single-hop data forwarding links x of all data network nodes 110 to be measured. XZZ 、x ZZY All explicit jump delays d H_XZZ d H_ZZY .

[0078] However, in principle, no explicit hop delays are exchanged between nodes, and there is no master / slave role in this regard. Each node is solely responsible for determining the round-trip delay to its neighboring nodes and, from this, calculating the necessary delay to adapt the forwarding path through the local node to the target delay pre-established in the system in terms of time.

[0079] After completing all single-hop data forwarding links and all single-hop data forwarding links to be measured x XBB 、x BBY The associated hop delay dH_XBB d H_BBY After the measurement of the master data network node 110M is designated to determine the common hop delay d CH In this case, a clear hop delay may be transmitted to the primary data network node 110M.

[0080] Therefore, in the case where the second data network node 110B operates as such a master data network node 110M, the initialization unit LCU prompts the second data network node 110B as the master data network node 110M to perform the following steps. Therefore, the second data network node 110B receives from the slave data network node 110S all single-hop data forwarding links x to be measured from the slave data network node 110S. XZZ 、x ZZY The respective explicit hop delay d H_XZZ d H_ZZY Since the master data network node 110M knows any and all hop delays of all single-hop data forwarding links of all slave data network nodes to be measured, the master data network node 110M specifies the common hop delay d according to the transmitted hop delays. CH The master data network node 110M is relatively free in terms of specification type; the only condition applied is the predetermined fixed common hop delay d CH Equal to the total transmitted hop delay d H_XZZ d H_ZZY The maximum value among them, or greater than all transmitted hop delays d H_XZZ d H_ZZY , because otherwise at least one of the transmitted hop delays will be greater than the fixed common hop delay d CH , so synchronization in the sense of the present invention would not be possible.

[0081] In addition to the common hop delay d CH Besides the fact that the common hop delay d must be greater than all hop delays of all single-hop data forwarding links in the network 10, it is further advantageous that the specified common hop delay d CH The difference in time period between the hop delay with the longest time period transmitted by the slave data network node 110S is chosen to be as small as possible in order not to pass an unnecessarily large common hop delay d CH Unnecessarily delaying data traffic within the synchronous data network system 10. Thus, a typical hop delay period in the avionics data network system 10 according to the present invention is in the range of 350 ns, where, for example, a specified common hop delay d of 500 ns is CH would be an acceptable value for the common hop delay. It should be emphasized that the figures mentioned are orders of magnitude only, since only a small portion of the delay is caused by the cable length. The majority of the delay is introduced by the transceiver and through the implementation of the node's network interface.

[0082] In the case of a fixed common hop delay d CH In the actual implementation, the fixed common jump delay d CH It can therefore correspond to a time period that is equal to the jump delay d with the longest time period scaled by a safety factor greater than 1 or by a safety offset. H_XZZ d H_ZZY . For example, the safety factor may correspond to a value greater than 1 and less than 1.5, less than 1.4, less than 1.3, less than 1.2 or less than 1.1 or less than 1.05. The safety bias may be in the range between 100 ns and 200 ns. It should be noted at this point that, as mentioned above, the cable length accounts for only a small portion of the total delay for data transmission on the data transmission link x in the network 10. The required range depends on the runtime variation (minimum value) and the resources used for the delay buffer (maximum value). In any case, the additional delay is typically low compared to the delay already introduced due to the transceiver and cable length. It is noteworthy that the effect of cable length on short transmission links (e.g. less than 10 m) is much smaller than the effect of the transceiver and interface structure of the node itself. In a prototype implementation, a total delay of approximately 300 ns was measured for a transmission link with a 3 m connecting cable, with the optical fiber causing a delay of approximately 5 ns / m.

[0083] In any case, the offset should be designed so that if the system is modified or if an additional cable section of 10 cm to 50 cm is inserted, the system does not have to be completely reconfigured and initialized again. The larger the offset selected, the more robust the data network system 10 is in the event of component changes in their delays. It should also be emphasized that discrete values ​​are of little significance in this context. The larger the safety offset, the greater the possible length changes, provided that the runtime variations are known.

[0084] Therefore, the safety offset only specifies the maximum compensation potential, but this does not mean that this potential must always be exhausted. Rather, it depends on the target network. Even in a system where node delays of up to 1 second can be variably added, it is still possible to operate with a maximum offset of 5ns. This is because all nodes have very low latency, which is determined before commissioning and then naturally set as the target latency. For example, after the system has been modified, it would be impossible to dynamically optimize the network. If any changes are made to the system, the common target latency must be redefined and communicated to all nodes.

[0085] like Figure 5 As depicted, the second data network node 110B, which is the master data network node 110M, has received any and all hop delays d of all single-hop forwarding links to be measured from the data network node 110S. H_XZZ dH_ZZY And the common hop delay d has been determined CH After that, the specified common hop delay d CH is transmitted to all slave data network nodes 110S, and then at the value d CH After being transmitted to these slave data network nodes 110S by the communication control unit LCU / CONFIG, the slave data network nodes 110S transfer the value d CH Stored in the memory of the delay matching unit LMU.

[0086] Since the delay matching unit LMU now stores any and all important delays in packet forwarding, i.e., the intrinsic node delay d SRX_B , common hopping delay d CH , and may involve the delay of each relevant single-hop forwarding link of the second data network node 110B, the delay matching unit LMU can now calculate the corresponding matching period d specific to the single-hop data forwarding link according to the data forwarding link. ARX The data packet RDP_fwd is then transferred to the delay buffer CDB, which then delays the data packet RDP_fwd accordingly. In this process, the delay buffer CDB can be a conventional FIFO (first-in, first-out) buffer, which temporarily buffers data and then reads and forwards it again after a predetermined delay period. Furthermore, the delay matching unit LMU is in data communication with the communication control unit LCU / CONFIG to communicate its delay matching status LMS to the LCU / CONFIG.

[0087] In the following text, the synchronization process of the synchronous data network system 10 according to the present invention will be described.

[0088] Since after the initialization process, the data forwarding delay on any route through the network is now the specified common deterministic hop delay d CH Since the local time of all nodes in the network is an integer multiple of , this situation can be used to perform a very simplified synchronization process of the local time of all nodes in the network with the local time of a specific master node with a master clock CLK_M. In this process, synchronization is implicitly performed by periodic packet transmissions from the timing master node to all other nodes, choosing an arbitrary route through the network. These packets can carry a timestamp (timestamp t) reflecting the local time at the timing master node that is current immediately at the start of the transmission. tx ). In addition, these data packets or synchronization data packets SDP may include a unique identifier of the timing master node as the sender address (node ​​ID) and may also indicate how many hops have been made on the current route through the network to the node currently receiving the packet (# hops).

[0089] Based on the synchronization data packet SDP transmitted by the timing master node, the current local time at the timing master node when the synchronization data packet arrives at the node is equal to the timestamp t included in the synchronization data packet SDP tx Add the number of hops h multiplied by the specified common deterministic hop delay d CH :

[0090] T master =t tx +d CH *h.

[0091] The method according to the present invention is an implicit synchronization method, wherein no specific protocol needs to be implemented to enforce time between the timing master and slave nodes in the network. This is because if synchronization occurs periodically or cyclically within a certain time window, any type of communication between the timing master and slave nodes can be synchronized implicitly. For example, a data packet SDP can be dedicated to synchronization of the entire data network, but it is also conceivable that synchronization data packet information containing a timestamp, hop count, and the node ID of the master data network node 110M can be inserted into the header at periodic intervals or cyclically within a specific time window of a normal data packet to the corresponding slave data network node 110S. The repetition period of the periodic transmission of the synchronization data packet SDP can be selected based on the accuracy requirements, the drift of the slave clock over time, and other factors.

[0092] Therefore, dedicated synchronization packets are only needed if there is no regular or recurring communication between the timing master node and other nodes in the network within a certain time window. Synchronization occurs implicitly via any data packet because the information required for synchronization is embedded in the respective packet header. Of course, these fields are only relevant when the source node corresponds to the timing master node. The synchronization packet SDP is then nothing more than an ordinary packet that does not necessarily carry data.

[0093] Each node uses the current effective local time as the TX timestamp t of all packets it generates tx . This is not affected in case of forwarding by subsequent nodes, only the number of hops h is increased. Each node is potentially able to assume the role of a timing master node. This is firmly configured in advance without any particular impact on the transmission behavior of the node. Only during reception is it important to obtain synchronization information only from packets originating from the timing master node (TX ID=master). This greatly abstracts the handling of time synchronization and no special control is required except for pre-specifying the roles and ensuring that the application layer schedules network traffic between the timing master node and all other nodes at regular intervals (which then implicitly ensures time synchronization in the network). The synchronization information consists of the TX timestamp t tx, a combination of the number of hops h and the TX ID (all of which may be transmitted, for example, as part of the packet header (field)), and a common deterministic hop delay period d stored locally at each node CH Specifically, if the second data network node 110B operates as a slave data network node 110S, the synchronization control unit CONFIG prompts the second data network node 110B to perform the following steps.

[0094] Therefore, the second data network node 110B receives a time stamp t having a master clock from the master data network node 110M having a master clock CLK_M. tx Then, as Figure 5 As depicted, after the synchronization data packet has been received by the data receiving unit RX, in accordance with the first exemplary embodiment or as Figure 3A or Figure 4A In the case of a single-hop data forwarding link, a synchronization packet SDP ( Figure 5 In the second exemplary embodiment (i.e., as Figure 3B and 4B In the case of a single-hop forwarding link, the delay buffer CDB does not need to occur ( Figure 5 path in (b)), this is because the specific delay matches the period d ARX The sum has already been performed by the preceding transmitting data network node 110 of the input transmission link x. The slave clock CLK_S of the second data network node 110B or 110S is then synchronized by means of the control of the communication control unit LCU / CONFIG. Thus, according to the number of completed hops h of the synchronization data packet SDP between the master data network node 110M and the second data network node 110B and by means of the common deterministic hop delay d CH , based on the formula t master =t tx +d CH *h, the slave clock CLK_S of the second data network node 110B is time synchronized with the master clock.

[0095] In case the second data network node 110B operates as the master data network node 110M, the synchronization control unit CONFIG prompts the second data network node 110B to perform the following steps. Thus, the synchronization control unit CONFIG ensures that at time t tx At , there will be a master clock timestamp t tx The synchronization data packet SDP is transmitted to the slave data network node 110S, and the synchronization data packet SDP includes the master clock timestamp t tx In addition, it may also include the hop count h and the identifier ID_M of the master data network node 110M.

[0096] According to the present invention, there is also provided a method for initializing the synchronous data network system 10, the method comprising: Figure 7 The following steps are depicted. Thus, in step S210, a round trip measurement command RTMR is transmitted from the communication control unit LCU of the slave data network node 110S to the data transmission unit TX of the slave data network node 110S. In step S220, the data transmission unit TX of the slave data network node 110S transmits a round trip measurement command RTMR via the single-hop data forwarding link x to be measured. XBB 、x BBY The respective direct data transmission link x transmits a round trip signal or a ping signal to the data receiving unit RX of the respective additional slave data network node 110S.

[0097] In this process, in step S230, the delay matching unit LMU of the slave data network node 110S starts the timer of the slave data network node 110S when transmitting the round-trip signal. After the data receiving unit RX of the slave data network node 110S receives (step S240) the round-trip signal sent back from the corresponding additional slave data network node 110S via the corresponding direct data transmission link x, in step S250, the delay matching unit LMU of the slave data network node 110S stops the timer when receiving the sent back round-trip signal. In step S260, the round-trip delay d is read from the timer of the slave data network node 110S. RT , and in step S270, by delaying the intrinsic node d SRX_B Add the round-trip delay d RT The single-hop data forwarding link x to be measured is calculated by taking half of XBB 、x BBY The specific hop delay d H_XBB d H_BBY . For all single-hop data forwarding links x to be measured XBB 、x BBY After repeating step (S280), all single-hop data forwarding links x to be measured are stored (S290). XBB 、x BBY The explicit jump delay d H_XBB d H_BBY .

[0098] Optionally, if a common hop delay based on all explicit hop delays of all single-hop data forwarding links to be measured is specified by the master data network node 110M during initialization, the following additional steps may be performed: In step S2100, all single-hop data forwarding links to be measured are set to XBB 、x BBY The explicit jump delay d H_XBB d H_BBYThe master data network node 110M has received all the single-hop data forwarding links x of the slave data network node 110S to be measured in step S2110. XZZ 、x ZZY The respective explicit hop delay d H_XZZ d H_ZZY Then, the slave data network node 110S receives the transmitted hop delay d in step S2120. H_XZZ d H_ZZY Specify the common hop delay d CH , where the predetermined fixed common hop delay d CH Greater than the total transmitted hop delay d H_XZZ d H_ZZY .

[0099] Figure 8 The present invention further illustrates a method for synchronizing a synchronous data network system 10 using at least one master data network node 110M and a slave data network node 110S, the method comprising the following steps:

[0100] Therefore, in step S310, the master data network node 110M performs the following operations at time t tx The master clock timestamp t is transmitted to the slave data network node 110S. tx In step S320, the slave data network node 110S receives a synchronization data packet SDP having a master clock timestamp t sent by the master data network node 110M having a master clock CLK_M. tx After the synchronization data packet SDP has been received, in step S330, the synchronization data packet SDP is synchronized with the master data network node 110M and the slave data network node 110S according to the number of completed hops h and the common deterministic hop delay d. CH , based on the formula t master =t tx +d CH *h, synchronizes the slave clock CLK_S of the slave data network node 110S with the master clock time.

[0101] According to the present invention, there is also provided a synchronous data network system 10, a master data network node 110M and a slave data network node 110S adapted to perform the above-mentioned initialization or synchronization method according to the present invention.

Claims

1. A synchronous data network system (10), comprising: A data network (100) connecting data network nodes (110) to each other for data exchange via direct bidirectional data transmission links (x) between adjacent data network nodes (110); The node chain of the data network node (110), the node chain is composed of a first data network node (110A), a second data network node (110B) and a third data network node (110C) in a row, wherein the second data network node (110B) is suitable for connecting to the data forwarding link (x ABBC ) receives a first direct data transmission link (x) from the first data network node (110A) between the first data network node (110A) and the second data network node (110B) AB ) and is suitable for a second direct data transmission link (x) between the second data network node (110B) and the third data network node (110C) BC ) forwards the data to the third data network node (110C) in a transmission mode, It is characterized in that The second data network node (110B) is adapted to enable a single-hop data forwarding link (x) between the first data network node (110A) and the third data network node (110C) ABB 、x BBC ) makes the data forwarding delay on the hop delay (d H_ABB ,d H_BBC ) is equal to the predetermined fixed common hopping delay (d CH ).

2. The synchronous data network system (10) according to claim 1, further comprising: A master data network node (110M) having a master clock (CLK_M), the master data network node (110M) being adapted to transmit a message having a master clock time stamp t to a slave data network node (110S) tx The invention relates to a synchronization data packet (SDP) and is suitable for completing the hop number h of the synchronization data packet (SDP) between the master data network node (110M) and the corresponding slave data network node (110S) and passing through a common hop delay period d. CH Based on the formula t master =t tx +d CH *h, so that the slave clock (CLK_S) of the slave data network node (110S) is synchronized with the master clock time.

3. The synchronous data network system (10) according to claim 1 or 2, characterized in that: The single-hop data forwarding link (x ABB 、x BBC ) corresponds to the data forwarding link (x ABB ), the data forwarding link (x ABB ) starting at the transmitter side of the first data network node (110A), via a direct data transmission link (x) between the first data network node (110A) and the second data network node (110B) AB ) passes through the second data network node (110B) and ends at the transmitter side of the second data network node (110B).

4. The synchronous data network system (10) according to claim 1 or 2, characterized in that: The single-hop data forwarding link (x ABB 、x BBC ) corresponds to the data forwarding link (x BBC ), the data forwarding link (x BBC ) starts at the receiver side of the second data network node (110B), passes through the second data network node (110B), via a direct data transmission link (x) between the second data network node (110B) and the third data network node (110C) BC ), and ends at the receiver side of the third data network node (110C).

5. The synchronous data network system (10) according to any one of the preceding claims, characterized in that The second data network node (110B) comprises: a data transmission unit (TX) connected to the direct data transmission link (x) for transmitting data (ODP) to other data network nodes (110); a data receiving unit (RX) connected to the direct data transmission link (x) to receive data (IDP) from other data network nodes (110); A delay matching unit (LMU) is adapted to store the current single-hop data forwarding link (x ABB 、x BBC )’s specific hop delay (d H_ABB ,d H_BBC ) and through a predetermined fixed common jump delay period (d CH ) to calculate the current single-hop data forwarding link (x ABB 、x BBC ) of the delay matching period (d ARX );as well as A delay buffer (CDB) is inserted between the data receiving unit (RX) and the data transmission unit (TX) to make the current single-hop data forwarding link (x ABB 、x BBC ) is forwarded with the specific delay matching period (d ARX )Delay.

6. The synchronous data network system (10) according to claim 5, characterized in that: The delay matching unit (LMU) comprises: Timer, used to measure the single-hop data forwarding link (x ABB 、x BBC ) round-trip delay (d RT ) to make measurements; Memory, used to store the intrinsic node delay (d SRX_B ), a single-hop data forwarding link (x) of the second data network node (110B) ABB 、x BBC ) of the round trip delay (d RT ) and the predetermined fixed common jump delay (d CH );as well as A calculation unit adapted to use the formula d ARX =d CH -d RT / 2-d SRX_B To calculate the delay matching period (d ARX ).

7. A synchronous data network system (10) according to any one of the preceding claims, characterized in that The second data network node (110B) comprises a communication control unit (LCU / CONFIG) for controlling initialization and synchronization, the communication control unit (LCU / CONFIG) comprising: an initialization control unit (LCU) for controlling an initialization process of the data network node (110); and A synchronization control unit (CONFIG) controls the synchronization of the data network node (110).

8. The synchronous data network system (10) according to claim 7, characterized in that: The initialization control unit (LCU) prompts the second data network node (110B) as the slave data network node (110S) to perform the following steps: transmitting a round trip measurement command (RTMR) from the communication control unit (LC) to the data transmission unit (TX); The data transmission unit (TX) transmits data via the single-hop data forwarding link (x XBB 、x BBY )'s corresponding direct data transmission link (x) transmits a round trip signal or a ping signal to a data receiving unit (RX) of a corresponding receiving data network node (110); The delay matching unit (LMU) starts a timer when transmitting the round-trip signal; The data receiving unit (RX) receives the round-trip signal sent back from the corresponding data network node (110) via the corresponding direct data transmission link (x); The delay matching unit (LMU) stops the timer when receiving the round-trip signal sent back; Read the round trip delay (d RT ); By taking the inherent node delay (d SRX_B ) plus the round trip delay (d RT ) to calculate the single-hop data forwarding link (x XBB 、x BBY )’s specific hop delay (d H_XBB ,d H_BBY ); For all single-hop data forwarding links to be measured (x XBB 、x BBY ) repeat these steps; and Store all single-hop data forwarding links to be measured (x XBB 、x BBY ) of the explicit jump delay (d H_XBB ,d H_BBY ).

9. The synchronous data network system (10) according to claim 7, characterized in that: The synchronization control unit (CONFIG) prompts the second data network node (110B) as the slave data network node (110S) to perform the following steps: Receive a master data network node (110M) having a master clock (CLK_M) with a master clock timestamp t tx Synchronous Data Packet (SDP); as well as According to the number of completed hops h of the synchronization data packet (DLP) between the main data network node (110M) and the second data network node (110B) and through a common deterministic hop delay period d CH Based on the formula t master =t tx +d CH *h, synchronize the slave clock (CLK_S) of the second data network node (110B) with the master clock time.

10. The synchronous data network system (10) according to claim 7, characterized in that: The synchronization control unit (CONFIG) prompts the second data network node (110B) as the master data network node (110M) to perform the following steps: at time t tx The slave data network node (110S) transmits a data packet having a master clock timestamp t tx The synchronization data packet (SDP) of 11. The synchronous data network system (10) according to claim 9 or 10, characterized in that: In addition to the master clock timestamp (t tx ), the synchronization data packet (SDP) also includes the hop count (h) and an identifier (ID_M) of the master data network node (110M).

12. The synchronous data network system (10) according to any one of the preceding claims, characterized in that The synchronized data network system is an avionics system data network for deterministic communication between the data network nodes (110).

13. A method for initializing a synchronous data network system (10), the method comprising the following steps: Transmitting (S210) a round trip measurement command (RTMR) from a communication control unit (LC) of a slave data network node (110S) to a data transmission unit (TX) of the slave data network node (110S); The data transmission unit (TX) of the slave data network node (110S) is transmitted via the single-hop data forwarding link (x XBB 、x BBY )'s corresponding direct data transmission link (x) transmits (S220) a round-trip signal or a ping signal to a data receiving unit (RX) of a corresponding additional slave data network node (110S); The delay matching unit (LMU) of the slave data network node (110S) starts (S230) the timer of the slave data network node (110S) when transmitting the round-trip signal; receiving (S240) the round-trip signal sent back from the corresponding additional slave data network node (110S) via the corresponding direct data transmission link (x) by a data receiving unit (RX) of the slave data network node (110S); The delay matching unit (LMU) of the slave data network node (110S) stops (S250) the timer when receiving the round-trip signal sent back; The round trip delay (d RT ); By taking the inherent node delay (d SRX_B ) plus the round trip delay (d RT ) to calculate (S270) the single-hop data forwarding link (x XBB 、x BBY )’s specific hop delay (d H_XBB ,d H_BBY ); For all single-hop data forwarding links to be measured (x XBB 、x BBY ) repeat (S280) these steps; and Store (S290) all single-hop data forwarding links (x XBB 、x BBY ) of the explicit jump delay (d H_XBB ,d H_BBY ).

14. A method for synchronizing a synchronous data network system (10), the synchronous data network system (10) comprising at least one master data network node (110M) and a slave data network node (110S), the method comprising the following steps: Through the master data network node (110M) at time t tx The slave data network node (110S) transmits (S310) a data packet having a master clock timestamp t tx Synchronization Data Packet (SDP), The slave data network node (110S) receives (S320) a master data network node (110M) having a master clock (CLK_M) with a master clock time stamp t tx Synchronization Data Packet (SDP), and According to the number of completed hops h of the synchronization data packet (SDP) between the master data network node (110M) and the slave data network node (110B) and the common deterministic hop delay period d CH Based on the formula t master =t tx +d CH *h, synchronize the slave clock (CLK_S) of the slave data network node (110S) with the master clock time (S330).

15. A synchronous data network system (10), comprising at least one master data network node (110M) and a slave data network node (110S), the synchronous data network system (10) being adapted to perform the method according to claim 13 or 14.

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