Synchronous data network system and its initialization and synchronization methods

Abstract

A synchronous data network system (10) comprising a data network (100) connecting adjacent data network nodes (110) to one another for data exchange via bidirectional direct data transmission links (x) between the adjacent data network nodes (110), comprising an arbitrary node chain of data network nodes (110) consisting of a first data network node (110A), a second data network node (110B) and a third (110C) data network node, wherein the second data network node (110B) is connected to the data transmission link (x) ABBC ) from the first data network node (110A) on the first direct data transmission link (x) between the first data network node (110A) and the second data network node (110B) AB ) and transmit the received data in a transmit mode to the third data network node (110C) over a second direct data transmission link (xBC) between the second data network node (110B) and the third data network node (110C), with a hop delay (d H_ABB , d H_BBC ) is the hop delay (d CH ) between the first data network node (110A) and the third data network node (110C). ABB , x BBC ) to delay transmission of data on the network, thereby realizing implicit time synchronization of the data network system.

Description

[Technical Field]

[0001] The present invention relates to a synchronous data network system, particularly a data network system used as an avionics data network for deterministic and potentially flight safety related communications between data network participants. Further, the present invention relates to a method for initializing and synchronizing a data network system. [Background technology]

[0002] The use of data network components in avionics systems often requires enabling or facilitating deterministic communication between participants in the avionics system data network. This is a strict requirement, for example, when communication is a critical part of function and directly or indirectly impacts flight safety. Deterministic in this context is an abstract term, described in the November 8, 2005, document "Integrated Modular Avionics (IMA) Development Guidance and Certification Considerations" (RTCA SC-200, EUROCAE WG-6) as "the ability to produce predictable results based on past operations, with those results occurring repeatedly within a specified time frame."

[0003] One way to achieve deterministic behavior of a data network implementation is to have complete control over the network's data traffic in time and space, making it possible to provide bandwidth guarantees for communications between any two parties within the network for strictly defined periods of time.

[0004] The key to achieving this is ensuring that each data network node in a data network system, connected to other data network nodes through the network via each direct data transmission link, has a common understanding of the current system time within a defined tolerance range when communicating via each direct data transmission link. Therefore, for a deterministic data network system to function, it is essential that all components of the data network or data network nodes are synchronized with each other and have a common time base. This common clock time can be achieved through various time synchronization tools, including industry-standard methods such as the Precision Time Protocol (PTP) and its extensions for modern, time-sensitive networks.

[0005] Industry-standard time synchronization (hereafter simply referred to as synchronization) methods are optimized for use in complex, dynamically changing open networks, requiring sophisticated methods to establish a common time reference among all participants. In contrast, avionics network systems are often not only off-the-shelf but also closed systems to limit complexity. In these situations, there is a need to find efficient synchronization methods and simpler means to verify deterministic behavior.

[0006] In contrast to avionics system data network standards known from the prior art (such as ARINC-664, Part 7, AFDX) and standards still under development (such as CAIN over TSN), the complexity of network components must be significantly reduced to reduce costs, simplify the network computing power used for synchronization, shorten the time required to achieve safety certification, and increase efficiency. Summary of the Invention

[0007] Therefore, the present invention aims to provide a synchronized data network system and a method for its initialization and synchronization, which can achieve low complexity of network components, reduced costs, greatly simplified computational power required for synchronization, reduced time required for security authentication, and improved efficiency.

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

[0009] According to the present invention, there is provided a synchronous network system including a data network connecting adjacent data network nodes to each other for data exchange via direct data transmission links between them. According to the present invention, a node chain is provided between these network nodes, comprising a first data network node, a second data network node, and a third data network node in succession. The second data network node is configured to receive data transmitted over the first direct data transmission link between the first and second data network nodes from the first data network node on the data transmission link, and to transmit the received data in a transmit mode to the third data network node over the second direct data transmission link between the second and third data network nodes. In this process, the second data network node can delay transmission of data over the single-hop data transmission link between the first and third data network nodes, the hop delay being equal to a predetermined fixed common hop delay.

[0010] Thus, when a data network node participating in the network transmits data from a sending data network node to a receiving data network node, the intervening transmitting data network nodes are designed to delay the transmission of the data such that the hop time period or hop delay is independent of network-specific or node-specific delays, but is uniformly or smoothed to an equal fixed hop delay for each transmitting node.

[0011] This delay slightly increases response time and transmission delay, but data throughput remains unchanged, and at the same time greatly simplifies network-wide synchronization. The simplest way to synchronize the slave clocks of subordinate data network nodes with the master clock is by incrementing the timestamp of the transmitted synchronization packet (which is usually a normal data packet with corresponding header information) from the master data network node by the number of hops multiplied by a fixed common hop delay when it arrives at the subordinate data network node.

[0012] The synchronization of data network systems described below can also be used in distributed data networks, provided that multiple network components have reliable master clocks. Thus, the present invention provides a highly redundant method for synchronizing data network systems for deterministic communication between network participants.

[0013] When the data network system is implicitly synchronized by a master data network node having a master clock, the master data network node sends a synchronization data packet with a master clock timestamp t tx The number of completed hops of the synchronous data packet, h, and the common hop delay period, d, are calculated based on the following formula (1): CH It is preferable to synchronize the slave clocks of the slave data network nodes to the master clock time in accordance with the master clock time. t master = t tx + d CH * h ··· Formula〈1〉

[0014] There are two possible ways to define a single-hop data transmission link to smooth out the common hop delay period.

[0015] Firstly, for example, a single-hop data transmission link may be defined to correspond to a data transmission link that starts at the sender side of a first data network node, passes through a direct data transmission link between the first data network node and a second data network node, passes through the second data network node and terminates at the sender side of the second data network node.

[0016] And secondly, for example, a single-hop data transmission link can be defined to correspond to a data transmission link that starts at the receiving side of a second data network node, passes through the second data network node, goes via a direct data transmission link between the second data network node and a third data network node, and terminates at the receiving side of the third data network node.

[0017] In an actual implementation of the synchronous data network system, the second data network node preferably comprises: a data sending unit connected to the direct data transmission link for sending data to other data network nodes; a data receiving unit connected to the direct data transmission link for receiving data from other data network nodes; a delay matching unit configured to calculate a specific delay matching period for the current single-hop data transmission link using a stored specific hop delay of the current single-hop data transmission link and a predetermined fixed shared hop delay period; and a delay buffer interposed between the data receiving unit and the data sending unit for delaying transmission of data packets on the current single-hop data transmission link based on the specific delay matching period received from the delay matching unit.

[0018] In this process, the delay matching unit advantageously comprises: a timer for measuring the round trip delay of the single-hop data transmission link to be measured; a memory for storing the intrinsic node delay, the round trip delay of the single-hop data transmission link of the second data network node and a predetermined fixed common hop delay; and a calculation unit capable of calculating the delay matching period using equation (2). d ARX = d CH -d RT / 2 - d SRX_B ··· Formula〈2〉

[0019] In the practical implementation of the initialization and synchronization of the data network system of the present 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 for controlling the initialization process of the data network node, and a synchronization control unit for controlling the synchronization of the data network node.

[0020] In this process, it is useful for the initialization control unit to prompt the second data network node, as a subordinate data network node, to perform the following steps: sending a round-trip measurement command from the communication control unit to the data sending unit; the data sending unit sending a round-trip signal or a ping signal to the receiving unit of the corresponding data receiving node via the corresponding direct data transmission link of the single-hop data transmission link to be measured; the delay matching unit starting a timer when the round-trip signal is sent; the data receiving unit receiving a returned round-trip signal from the corresponding data network node via the corresponding direct data transmission link; the delay matching unit stopping the timer when the returned round-trip signal is received; reading the round-trip delay from the timer; calculating the specific hop delay of the single-hop data transmission link to be measured by adding the intrinsic node delay to half the round-trip delay; repeating the above steps for all single-hop data transmission links to be measured; and storing the confirmed hop delays of all single-hop data transmission links to be measured.

[0021] If during initialization a common hop delay is determined by the master data network node from the confirmed hop delays of all single-hop data transmission links being measured, an additional step is performed of transmitting the confirmed hop delays of all single-hop data transmission links to the master data network node, if necessary.

[0022] When the second data network node operates as a master data network node, the initialization control unit configures the second data network node as a subordinate data network node, receiving from the subordinate data network nodes the respective ascertained hop delays of the single-hop data transmission links of all the subordinate data network nodes to be measured; and identifying a common hop delay from the transmitted hop delays, where the predetermined fixed common hop delay is greater than all transmitted hop delays; It is beneficial to encourage them to do the following.

[0023] To ensure that the selected fixed common hop delay is not unnecessarily large, it is useful for the common hop delay to correspond to a period of time equal to the longest hop delay multiplied by a safety factor or safety offset greater than one.

[0024] When the data network system is synchronized by a second data network node acting as a slave data network node, the synchronization control unit transmits to the second data network node, as a slave data network node, a master clock timestamp t tx and receiving a synchronization data packet having a completed hop count h of the synchronization data packet between the master data network node and the second data network node and a common deterministic hop delay period d based on Equation 1. CH and synchronizing the slave clocks of the second data network nodes to the master clock time in accordance with the master clock time.

[0025] When the second data network node operates as a master data network node, the synchronization control unit controls the second data network node to operate as a master data network node at time t tx At master clock timestamp t tx It is advantageous to prompt the subordinate data network node to transmit a synchronization data packet having the following:

[0026] In order to easily make the hop count with the master clock timestamp available to the subordinate data network nodes and to ensure that synchronization occurs by authenticated synchronization of the master's data packets, it is highly advantageous if the synchronization data packets include the hop count and an identifier of the master data network node in addition to the master clock timestamp.

[0027] The synchronous data network system according to the present invention has significant advantages over the prior art when used as an avionics data network for deterministic and / or flight safety related communications between data network nodes, and is useful in this process when the data network has a ring, star or network structure with bidirectional data exchange.

[0028] Furthermore, according to the present invention, the initialization method for a synchronous data network system of the present invention includes the steps of: sending a round trip measurement command from a communication control unit of a subordinate data network node to a data sending unit of the subordinate data network node; sending a round trip signal or a ping signal by the data sending unit of the subordinate data network node to a data receiving unit of a corresponding additional subordinate data network node via a corresponding direct data transmission link of the single-hop data transmission link to be measured; starting a timer of the subordinate data network node when the delay matching unit of the subordinate data network node sends the round trip signal; receiving a round-trip signal returned from a corresponding additional subordinate data network node via a corresponding direct data transmission link by a data receiving unit of the data network node; stopping a timer by a delay matching unit of the subordinate data network node upon receiving the returned round-trip signal; reading a round-trip delay from the timer of the subordinate data network node; calculating a specific hop delay of the single-hop data transmission link to be measured by adding an intrinsic node delay to half the round-trip delay; and repeating the above steps for all single-hop data transmission links to be measured; and storing the ascertained hop delays of all single-hop data transmission links being measured.

[0029] Furthermore, according to the invention, if during initialization the master data network node defines a common hop delay from all ascertained hop delays of all single-hop data transmission links to be measured, then, if necessary: an additional step of transmitting the ascertained hop delays of all single-hop data transmission links being measured to a master data network node; an additional step of the master data network node receiving the respective ascertained hop delays of the single-hop data transmission links of all subordinate data network nodes to be measured; The master data network node may perform the additional step of specifying a common hop delay from the transmission hop delays. Here, the predetermined fixed common hop delay is greater than all transmission hop delays.

[0030] Furthermore, a method for synchronizing a synchronous data network system in the present invention includes at least one master data network node and a subordinate data network node, time t tx , the master clock timestamp t tx transmitting a synchronous data packet having From the master data network node having the master clock, through the subordinate network node, the master clock timestamp t tx and receiving a synchronization data packet having a completed hop count h and a common deterministic hop delay period d between the master data network node and the subordinate data network node according to Equation 1. CH and synchronizing the slave clocks of the slave data network nodes to the master clock time according to the master clock time.

[0031] According to the present invention, the synchronous data network system, the master data network node and the subordinate data network node are each configured to implement the above method. [Brief explanation of the drawings]

[0032] [Figure 1] 1 shows a highly simplified schematic diagram of a ring-structured synchronous data network system according to the present invention; [Figure 2]1 shows a node chain of first, second and third data network nodes connected to each other by first and second direct data transmission links. [Figure 3A] 4 shows a time flow chart of data delay through a second data network node according to the first embodiment of the present invention; [Figure 3B] 10 shows a time flow chart of delay of data through a second data network node according to a second embodiment of the present invention; [Figure 4A] 3 illustrates a node chain of first, second, third and fourth data network nodes illustrating delays in data transmission due to synchronization according to a first embodiment of the present invention. [Figure 4B] 5 shows a second, third, fourth and fifth data network node chain according to a second embodiment of the present invention, illustrating the time course of delays in data transmission for synchronization purposes; [Figure 5] 1 shows a schematic block diagram of a highly simplified data network node according to the present invention; [Figure 6A] 1 is a diagram illustrating the components of a data network node and their roles in the initialization of a synchronous data network system according to the present invention; [Figure 6B] 1 is a diagram illustrating the components of a data network node and their roles in the initialization of a synchronous data network system according to the present invention; [Figure 7] 1 shows a flow diagram illustrating a method for initializing a synchronized data network system in accordance with the present invention; [Figure 8] 1 shows a flow diagram illustrating a synchronization method for a synchronous data network system according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0033] The invention will now be described by way of example with reference to the accompanying drawings, in which corresponding elements in the various figures are given the same reference numerals.

[0034] 1 illustrates an example of a synchronous data network system 10 according to the present invention. The synchronous data network system 10 includes a data network 100 that connects adjacent data network nodes 110 to one another via direct data transmission links x between the adjacent data network nodes 110 for the purpose of data exchange. The data network system 10 may include, for example, as shown in FIG. 1, data network nodes 110A, 110B, 110C, and 110D that are connected to one another via direct data transmission links x. AB , x BC、 x CD and x AD The data network system 10 illustrated in FIG. 1 has a ring structure, but the data network 100 may have a star structure or a network structure. The present invention can be implemented in any network topology and is not limited to a specific network topology. Therefore, the topology of the network structure is free as long as the connections between nodes are bidirectional and at least one node has one or more interfaces to neighboring nodes so that a topology with two or more participants can be created. The number of data network nodes 110 is also arbitrary, and the four data network nodes 110A, 110B, 110C, and 110D illustrated in FIG. 1 should be understood as merely an example.

[0035] In the data network system 10, off-the-shelf avionics components are preferably provided as data network nodes 110 to enable deterministic and potentially flight-safety-related communication between avionics components as data network nodes via the avionics system data network. Such deterministic communication is essential, particularly within flight networks or when using autonomous flight or driving applications, where flight safety certification, and of course flight safety itself, requires synchronous communication and traceability of causality in avionics systems, particularly when these systems are utilized when the protection of human life, the performance of military missions, or the transport of high-value physical assets is at stake. Avionics components for use as data network nodes 110 within the context of the present invention may include a variety of avionics components, such as flight control and mission management computer systems, human-machine interfaces such as displays and input devices, flight attitude sensors, engine sensors and actuators, tail sensors and actuation, or weapons systems capable of firing weapons or decoys via the synchronous data network system. Although use in avionics is particularly preferred, the use of the synchronous data network system according to the present invention is not limited thereto, but can also be used in the fields of, for example, marine engineering, aerospace engineering such as satellite systems, or safety-related large-scale plants.

[0036] In the data network system 10 according to the present invention, a direct data transmission link x between two data network nodes 110 allows bidirectional or duplex unidirectional communication. The time behavior of data transmitted over the network 100 is governed by a unidirectional hop delay d as the master. H and the combined round-trip delay d RT , and each link depends on external factors such as the physical medium and environmental conditions, and internal factors such as the design and implementation of the data network node 110.

[0037] Hop delay d across the data network system 10 H Due to variations in the delays, the execution time of a data packet transmission from a source data network node 110 to a final recipient data network node 110 is not a direct function of the data transmission link selected by the data network 100 and the number of hops on this data transmission link. Rather, all specific delays caused by external or internal network factors must be taken into account, which would require a significant computational effort if the data network system 10 were to be implicitly synchronized. In this case, implicit synchronization means synchronizing all network node slave clocks to the master clock of the master data network node 110M (FIG. 5) by sending a synchronization data packet from the master data network node 110M to the data network node 110.

[0038] Furthermore, such synchronization is not only computationally intensive but also impacts the determinism of the system, since it relies on runtime initialization and therefore requires tolerances across a range of runtime-dependent values.

[0039] 2, the synchronous data network system 10 according to the invention is depicted in more detail, and the various delays introduced by the data network nodes 110 or the direct data transmission link x are now explained in more detail. FIG. 2 shows a node chain of data network nodes 110, which chain is made up of successive first, second and third data network nodes 110A, 110B and 110C, and when transmitting data from data network node 110A to data network node 110C, the delays are introduced by the direct data transmission link x. AB and x BC Direct transmission link x CB and x BA Although bidirectional communication is also possible via data network node 110A, only the transmission direction from data network node 110A to data network node 110C is shown for simplicity.

[0040] According to the invention, the second data network node 110B is connected to the data transmission link x ABBC From the first data network node 110A on the first direct data transmission link x between the first data network node 110A and the second data network node 110B AB and transmits the received data over a second direct data transmission link x between the second data network node 110B and the third data network node 110C. BC Then, it is transmitted to the third data network node 110C.

[0041] Thus, according to the present invention, there is a direct data transmission link x that is part of the data network 100 and a data transmission link x that constitutes a transmission link via a data network node 110 with a corresponding inherent nodal delay. ABBC A distinction should be made between

[0042] In particular, single-hop data transmission links x AAB , x ABB , x BBC , x BCC , or x in the following XZZ , x ZZY The hop-to-hop data transmission link, collectively referred to as a hop-to-hop link, is important to the present invention because it is the smallest unit of a data transmission hop from one data network node 110 to another data network node 110. There are two possible approaches to defining a single-hop data transmission link:

[0043] (a) A single-hop data transmission link is a data transmission link x ABB , x BCC In this case, the direct data transmission link x from the sender data network node 110A to the transmitting data network node 110B can be defined to correspond to ABand the data transmission link through data network node 110B are combined as a single-hop data transmission link. When data network node 110C is the transmitting data network node 110, the direct data transmission link x BC and the data transmission link passing through the data network node 110C is a single-hop data transmission link x BCC Therefore, when the second data network node 110B is the transmitting data network node 110, the single-hop data transmission link is the data transmission link x ABB which corresponds to the direct data transmission link x starting from the transmitting side of the first data network node 110A and connecting the first data network node 110A and the second data network node 110B. AB , through the second data network node 110B, and terminates at the transmitting side of the second data network node 110B.

[0044] (b) According to a second embodiment, a single-hop data transmission link x AAB , x BBC is a transmission link with a delay corresponding to the transmitting node 110 and a subsequent direct data transmission link x that transmits data originating from the transmitting data network nodes 110A and 110B to the corresponding additional data network nodes 110B and 110C, respectively. AB , x BC Therefore, when the second data network node 110B is a data transmission node, the single-hop data transmission link is the data transmission link x BBC , starting from the receiving side of the second data network node 110B, passing through the second data network node 110B, and connecting to the direct data transmission link x between the second data network node 110B and the third data network node 110C. BC and terminates at the receiving side of the third data network node 110C.

[0045] 2, a corresponding delay is assigned to the corresponding transmission link through the data network node 110 and the direct data transmission link x. This delay corresponds to the execution time or delay d when data is transmitted through the data network node 110. SRX_A , d SRX_B , d SRX_C Related to or delayed AB and d BC Direct data transmission link with x AB and x BC The time it takes to send data through the network is either related to the execution time or the delay when data is sent through the network.

[0046] For a single-hop data transmission link, the hop delay d H_AAB , d H_ABB , d H_BBC , and d H_BCC is the intrinsic node delay d SRX and the sum of the transmission delays over direct data transmission link x. Although the hop delays in Figure 2 are all drawn to be of equal magnitude, known data network systems 10 suffer from variations in intrinsic node delays and transmission delays that significantly complicate implicit synchronization of the data network systems 10.

[0047] However, this problem is overcome by a synchronous data network system 10 according to the present invention, as shown, for example, in Figures 3A and 3B. Figure 3A is a detailed view of Figure 2, illustrating the delay in data transmission in a first embodiment. The portion of Figure 2 depicted in Figure 3B illustrates the delay in data transmission according to a second embodiment of the present invention.

[0048] As shown in FIG. 3A, the second data network node 110B connects the single-hop data transmission link x between the first data network node 110A and the third data network node 110C. ABB is configured to delay the transmission of data over a hop delay d H_ABB is a given fixed common hop delay d CHIn this process, the single-hop data transmission link is configured to be equal to the data transmission link x ABB This corresponds to starting from the transmitting side of the first data network node 110A and connecting the direct data transmission link x between the first data network node 110A and the second data network node 110B. AB , through the second data network node 110B, and terminates at the transmitting side of the second data network node 110B.

[0049] In FIG. 3B, the second data network node 110B is connected to the single-hop data transmission link x between the first data network node 110A and the third data network node 110C. BBC is configured to delay the transmission of data over a hop delay d H_BBC is given a fixed common hop delay d CH In this process, the single-hop data transmission link is configured to be equal to the data transmission link x BBC which corresponds to a direct data transmission link x between the second data network node 110B and the third data network node 110C, starting from the receiving side of the second data network node 110B, passing through the second data network node 110B, and BC and terminates at the receiving side of the third data network node 110C.

[0050] For completeness, a first embodiment (a) (FIG. 3A) and a second embodiment (b) (FIG. 3B) are shown, with the first embodiment (a) being preferred due to the somewhat more difficult practical implementation of the second embodiment (b). In particular, in the second embodiment shown in FIG. 3B, locally generated outgoing packets must be generated in the RX path of the second data network node 110B, time-stamped, and delayed towards the outgoing link TX of the second data network node 110B. This delays data transmissions between adjacent nodes 110 that do not need to be delayed. (See also the paths IDP to RDP_loc and IDP to RDP_fwd_AC shown in FIG. 5).

[0051] According to the present invention, the intrinsic node delay d SRX_B is a variable node delay d AX_ABB or d AX_BBC This reduces the data transmission link delay d AB or d BC , and the intrinsic node delay d in the transmission hop through the second data network node 110B. SRX_B Regardless of the transmission execution time or transmission delay or single-hop data transmission delay d H_ABB or d H_BBC is always a predetermined common hop delay d in the synchronized data network system 10, regardless of which data network node 110 or which associated direct data transmission link x of the selected single-hop data transmission link is selected. CH becomes equal to

[0052] Delay circuits in the second network node 110B and all other transmitting data network nodes 110 delay data transmissions within the data network system 10 according to the present invention, an approach that greatly simplifies synchronization of the entire data network system 10. This is shown in Figure 4A for the first embodiment and in Figure 4B for the second embodiment.

[0053] Thus, synchronization of the data network system 10 according to the present invention can be achieved, for example, by using a master data network node 110M (FIG. 5) to synchronize corresponding subordinate data network nodes 110S of the data network system 10 with a master clock CLK_M (FIG. 5). To this end, the master data network node 110M synchronizes the master clock timestamp t tx and transmit a synchronization data packet SDP having the following to the subordinate data network node 110S, and calculate the number of completed hops h and the common hop delay period d of the synchronization data packet SDP between the master data network node 110M and each subordinate data network node 110S according to the formula 〈1〉. CH and synchronizes the slave clock CLK_S of the slave data network node 110S to the master clock time of the master data network node 110M according to the above.

[0054] This simple synchronization is made possible by the fact that, as shown in Figures 4A and 4B, the transmission of synchronization data packets SDP from data network nodes 110A to 110D (Figure 4A) or from data network nodes 110B to 110E (Figure 4B) has a well-defined time period that is synchronized from the master data network node 110M to the subordinate data network node 110S. That is, the number of hops from the master network node 110M to each subordinate data network node 110S is multiplied by a predetermined fixed common hop delay period d CH The number is multiplied by the data transmission link x AB , x BC , x CD , x DE can be of various nature and may be, for example, a cable-free or wireless direct data transmission link x in addition to a wired or cabled or fiber optic connection. Furthermore, regardless of the choice of data network node 110, the hop delay during data transmission is always a predetermined fixed common hop delay d CH The inherent node delay dSRX may also be different.

[0055] Although synchronization of the data network system 10 by a master data network node 110M according to the invention is preferred, it should be emphasized that synchronization is also possible in a distributed data network system if several network nodes are equipped with clocks suitable as master clocks. For example, instead of providing a single master data network node 110M, several data network nodes 110, or even all data network nodes 110, could act as master data network node 110M. This configuration maximizes the fault tolerance and redundancy of the synchronized data network system 10 according to the invention. In this case, only the corresponding coordination between the data network nodes 110 is required, ensuring that no two data network nodes 110 simultaneously assume the role of master.

[0056] The synchronization method according to the invention therefore makes it possible to conveniently achieve synchronization of all data network nodes with a hop delay that is identical for all data network nodes and corresponding transmission links and common for all connections within the closed network.

[0057] Figure 5 shows a block diagram of a data network node 110 according to the present invention. In this case, for example, the second data network node 110B comprises a data sending unit TX, which is connected to a direct data transmission link x for sending data ODP to another data network node 110, which is either a locally generated data packet TDP_loc to be sent or a transmitted data packet RDP_fwd to be sent. The second data network node 110B further comprises a data receiving unit RX, which is connected to a direct data transmission link x for receiving data IDP from another data network node 110. As shown in Figure 5, the second data network node 110B further comprises a data receiving unit RX, which is connected to a current single-hop data transmission link x for receiving data IDP from the other data network node 110.ABB , x BBC The stored specific hop delay d H_ABB , d H_BBC and a predetermined fixed common hop delay period d CH and the current single-hop data transmission link x ABB , x BBC A specific delay matching period d ARX When transmitting a data packet IDP from the data receiving unit RX to another data network node 110 via the data sending unit TX, the data packet RDP_fwd (e.g., RDP_fwd_AC or RDP_fwd_CA) is transmitted between the data receiving unit RX and the current single-hop data transmission link x ABB , x BBC The data packet RDP_fwd_CA is sent from the data delay matching unit LMU for a specific delay matching period d ARX The data passes through a delay buffer CDB, which is interposed between the data transmission unit TX and the data designated for transmission, which is delayed based on the delay buffer CDB.

[0058] The structure of the delay matching unit LMU is shown in Figure 6A. The delay matching unit LMU is ABB , x BBC Round-trip delay d RT and a timer to measure the intrinsic node delay d SRX_B , the single-hop data transmission link x of the second data network node 110B ABB , x BBC Round-trip delay d RT and a given fixed common hop delay d CH Furthermore, the delay matching unit LMU has a memory for storing a delay matching period d specific to the single-hop data transmission link. ARX_ABB The device includes a calculation unit configured to calculate using Equation 2:

[0059] As shown in Fig. 5, delays of data packets only occur if they are designated for transmission, whereas received data packets RDP_loc that are not synchronous data packets and are designated for further local processing in the corresponding second data network node 110B are not delayed. Therefore, in the first embodiment of the invention, a configurable data transmission delay is preferably provided at the receiving side of each node only for packets that have not yet reached their destination address and are sent to the data sending unit TX for transmission from the data receiving unit to the data sending unit. In this way, packets that are further processed locally can be sent quickly and directly to the end user without any further delay, in contrast to the implementation according to the second embodiment of the invention, where a delay occurs at the sending side where the transmission link covers up to the next data network node 110.

[0060] 5, the second data network node 110B has either a master clock CLK_M or a slave clock CLK_S, depending on whether the second data network node 110B operates as a master data network node 110M or as a slave data network node 110S. When the second data network node 110B operates as a slave data network node 110S, the slave clock CLK_S is synchronized with the master clock CLK_M of the other master data network node 110M by the data packet SDP, without any delay following reception in the second embodiment of the present invention or after a delay by the delay buffer CDB in the first embodiment. The second data network node 110B further comprises a communication control unit LCU / CONFIG for controlling initialization and synchronization, the communication control unit LCU / CONFIG comprising an initialization control unit LCU that controls the initialization process of the data network node 110, and a synchronization control unit CONFIG that controls the synchronization of the data network node 110.

[0061] The process of initializing a synchronous data network system according to the present invention and the subsequent process of synchronizing the data network 10 according to the present invention will now be described.

[0062] During network initialization, all nodes in the network are required to independently determine the delays of all data transmission links to adjacent nodes in the network. In this process, the interface implementation of the data network nodes must be symmetric or have a known asymmetry considering the adjacent nodes. Therefore, hop delays can be accurately derived from round-trip delay measurements. Before network initialization is complete, each node must add additional delays or specific delay matching periods d to all data transmission links and data reception paths associated with connections to adjacent nodes. ARX This ensures that the hop delays of these connecting links correspond to a common value that can be configured across the network, and this value is determined from the single-hop data transmission delay before the network goes live. This value is determined by a predetermined fixed common hop delay d CH or the common deterministic hop delay d CH is.

[0063] It should be emphasized that network initialization is fully decentralized, and the distinction between subordinate and master data network nodes 110M is initially irrelevant. This is because the subsequent master data network node 110M also initially undergoes the same initialization process as all other data network nodes 110, as a subordinate data network node 110S. That is, all nodes determine the round-trip delay to their neighboring nodes as part of the network initialization (generating requests, receiving responses, and receiving requests and generating responses). At this point, there is no role; all nodes are equal. As soon as each node determines the information it needs, the target delay is set and the initialization phase ends. The uniform hop delay allows implicit time synchronization, simply by the defined master periodically communicating with all other nodes (one-way, no response required).

[0064] As shown in Figures 6A and 6B, initialization specifically proceeds as follows in an exemplary probe of a single-hop data transmission link to an adjacent data network node 110A from the perspective of the second data network node 110B acting as a subordinate data network node 110S:

[0065] Therefore, the initialization control unit LCU prompts the second data network node 110B, acting as the subordinate data network node 110S, to perform the following steps during the initialization process of the synchronous data network system 10: First, the communication control unit LCU sends a round trip measurement command RTMR to the data sending unit TX. Then, the data sending unit TX sends a round trip measurement command RTMR to the data receiving unit RX of the corresponding receiving data network node 110A via the corresponding direct data transmission link x, e.g., the single-hop data transmission link x to be measured in the first embodiment of the present invention. ABB If so, direct data transmission link x AB6B). At the same time as the round trip signal is transmitted, the delay matching unit LMU starts a timer of 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 is transmitted again directly via the data sending unit TX of the data network node 110A to the receiving unit RX of the second data network node 110B via the corresponding direct data transmission link x from the corresponding first data network node 110A. AB Upon receiving the returned round trip signal via the delay matching unit LMU, the delay matching unit LMU stops the timer upon receiving the returned round trip signal.

[0066] As illustrated in FIGS. 6A and 6B, the timer of the delay matching unit LMU calculates the round trip delay d RT After reading, the delay matching unit LMU calculates the intrinsic node delay d SRX_B The round trip delay d RT Adding half of this to the single-hop data transmission link x under test ABB The specific hop delay d H_ABB Calculate the inherent node delay d SRX_B can be ascertained by the second data network node 110B itself by internally measuring the internal transmission delay of the data packets from the data receiving unit RX to the data sending unit TX. This intrinsic node delay value may also be measured when the involved data network node is established and saved or stored in the memory of the delay matching unit LMU.

[0067] The second data network node 110B may, for a complete initialization of the initialized data network system 10, reset any single-hop data transmission link x according to the first or second embodiment. XBB , xBBY Therefore, the initialization process described above is repeated until the second data network node 110B has measured all single-hop data transmission links directly connected to the data network node 110.

[0068] If the "worst case" hop delay has already been determined during the platform validation phase, this hop delay can be calculated as the given common hop delay d CH The configuration is notified to each data network node 110 as follows.

[0069] However, to optimize the overall delay, the network must consider the common hop delay d CH It is also possible to dynamically check the single-hop data transmission links x of all data network nodes 110 to be measured, which can be done, for example, via the master data network node 110M, but also using an external reader that is connected to the network once during initialization. XZZ , x ZZY All confirmed hop delays d H_XZZ , d H_ZZY can also be read out.

[0070] However, in principle, nodes do not exchange confirmed hop delays, and there is no master / subordinate role in this respect. Each node is solely responsible for determining the round-trip delay to its neighboring nodes and for calculating the delay required to adapt the transmission path through the local node in time to a target delay previously established in the system.

[0071] All single-hop data transmission links and All single-hop data transmission links x XBB , x BBY All the measured associated hop delays d H_XBB , d H_BBY and the common hop delay d CHIf the master data network node 110M is designated in the determination, the identified hop delay may be transmitted to the master data network node 110M.

[0072] Therefore, if the second data network node 110B acts 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: The second data network node 110B then transmits from the subordinate data network nodes 110S the single-hop data transmission links x XZZ , x ZZY , respectively confirmed hop delay d H_XZZ , d H_ZZY Since the master data network node 110M knows all the hop delays of all the single-hop data transmission links of all the subordinate data network nodes to be measured, the master data network node 110M can calculate the common hop delay d from the transmitted hop delays. CH The master data network node 110M is relatively free to specify the type of assignment. The only condition for it to be applicable is a predetermined fixed common hop delay d CH is the total hop delay d H_XZZ , d H_ZZY If this is not the case, then at least one transmission hop delay must be greater than or equal to the fixed common hop delay d CH , and therefore synchronization according to the present invention becomes impossible.

[0073] Common hop delay d CH In addition to the fact that must be larger than all hop delays of all single-hop data transmission links in the network 10, there is an unnecessarily large common hop delay d CHTo avoid unnecessary delays in data traffic within the synchronous data network system 10 due to a specified common hop delay d CH It is further advantageous if the difference in time period between d and the hop delay with the longest time period transmitted by the subordinate data network node 110S is selected as small as possible. Thus, typical hop delay periods in the avionics data network system 10 according to the present invention are in the range of 350 ns, with a specified common hop delay d of, for example, 500 ns as the common hop delay tolerance. CH It should be emphasized that the above figures are only estimates and that most of the delay is not caused by the length of the cable. Most of the delay is caused by the transceiver and the implementation of the node's network interface.

[0074] fixed common hop delay d CH In practical implementations, the fixed common hop delay d CH is the longest hop delay d H_XZZ , d H_ZZYThe delay can correspond to a time period equal to the time multiplied by a safety factor or safety offset of at least 1. For example, the safety factor can correspond to values ​​greater than 1 and less than 1.5, 1.4, 1.3, 1.2, 1.1, or 1.05. The safety offset can range from 100 ns to 200 ns. It should be noted at this point that the delay due to the cable length mentioned above should only be a small fraction of the overall delay of data transmission in network 10 on data transmission link x. The required range depends on the variation in execution time (minimum) and the resources used for delay buffers (maximum). In any case, the additional delay is usually small compared to the delay already introduced by the transceivers and cable length. It should be noted that cable length has a much smaller impact on short transmission links (e.g., less than 10 m) than the interface structure and the transceivers in the node itself. In a prototype implementation, the total delay of a transmission link constructed using a 3 m connecting cable was approximately 300 ns, of which approximately 5 ns / m was due to the optical fiber.

[0075] In any case, the offset should be designed so that if the system is modified or 10 cm to 50 cm of cable is added, the system does not have to be completely reconfigured and reinitialized. The larger the selected coefficient, the more robust the data network system 10 will be when component delays are changed. It should also be emphasized that discrete values ​​have little meaning in this case. The larger the safety offset, the larger length changes are allowed when run-time variations are known.

[0076] Therefore, the safety offset only defines the maximum compensation possible, but it does not necessarily mean that it must always be maximized. Rather, it depends on the network in question. Even in a system where node delays can be variably added up to 1 second, it is possible to operate with a maximum offset of 5 ns if the delays of all nodes are very low, determined before operation begins, and naturally set as the target delay. For example, it should not be possible to dynamically optimize the network after a system change. If there is a change in the system, a common target delay must be newly determined and transmitted to all nodes.

[0077] Then, as shown in FIG. 5, the second data network node 110B as the master data network node 110M measures all the hop delays d of the single-hop transmission links of all the subordinate data network nodes 110S to be measured. H_XZZ , d H_ZZY receive, and the common hop delay d CH Once the specified common hop delay d CH is transmitted to all subordinate data network nodes 110S. The value d CH is transmitted to all 110S by the communication control unit LCU / CONFIG and then stored in the memory of the delay matching unit LMU.

[0078] The delay matching unit LMU is responsible for matching any significant delay in the transmission of data packets, i.e. the intrinsic node delay d SRX_B , common hop delay d CH , and the delay of each associated single-hop transmission link that the second data network node 110B may be involved in, the delay matching unit LMU then stores, depending on the data transmission link, a corresponding matching period d specific to the single-hop data transmission link. ARXand sends it to the delay buffer CDB, which delays the data packet RDP_fwd accordingly. In this process, the delay buffer CDB may be a normal FIFO buffer (First In First Out), which buffers the data for a short time and reads it out again to send it after a predetermined delay period. Furthermore, the delay matching unit LMU is in data connection with the communication control unit LCU / CONFIG for communicating the delay matching status LMS to the communication control unit LCU / CONFIG.

[0079] The synchronization process of the synchronous data network system 10 according to the present invention will now be described.

[0080] After the initialization process, the data transmission delay on any path through the network is a specified common deterministic hop delay d CH , so this situation can be used to perform a very simplified synchronization procedure that synchronizes the local time of all nodes in the network to the local time of a specific master node with the master clock CLK_M. In this process, the timing master node periodically sends packets to all other nodes, implicitly achieving synchronization. An arbitrary route in the network can be selected for this purpose. At the start of transmission, a timestamp (timestamp t tx Additionally, these data packets or synchronization data packets SDP may contain a unique identifier of the timing master node as the source address (node ​​ID) and may also indicate how many hops have been taken on the current route through the network to the node currently receiving the packet.

[0081] Based on the synchronization data packet SDP sent by the timing master node, the local time of the timing master node when the synchronization data packet arrives at the node is the timestamp t included in the synchronization data packet SDP. tx , given a common deterministic hop delay d CH is equal to the sum of the product of the number of hops h and the number of hops m.

[0082] This method according to the present invention is an implicit synchronization method, which means that no specific protocol is required to implement the time interval between the timing master and the subordinate nodes. This is because synchronization can occur implicitly for any type of communication between the timing master and the subordinate nodes, provided that it is performed periodically or repeatedly within a specific time frame. For example, the data packet SDP can be dedicated to synchronization of the entire data network, but synchronization data packet information, including the timestamp, hop count, and node ID of the master data network node 110M, can also be inserted into the header of a regular data packet to the corresponding subordinate data network node 110S periodically or repeatedly within a specific time window. The recurrence period of the periodic transmission of the synchronization data packet SDP can be selected depending on the accuracy requirements, the drift of the subordinate clocks over time, and other factors.

[0083] Therefore, dedicated synchronization data packets are only needed if there is no regular or recurring communication between the timing master and other nodes in the network within a certain time frame. Synchronization is implicit in any data packet, since the information required for synchronization is embedded in each packet header. Of course, these fields are only relevant if the source node corresponds to the timing master. Synchronization data packets (SDP) do not necessarily carry data; they are just regular packets.

[0084] Each node generates a TX timestamp t txThe currently valid local time is used as the timestamp. This is not affected when subsequent nodes transmit, and only the hop count h increases. Each node has the potential to assume the role of Timing Master. This is firmly set in advance without any particular impact on the node's transmission behavior. It is important that, on reception only, synchronization information is obtained only from packets originating from the Timing Master (TX ID = Master). This makes the process of time synchronization largely abstract and no special control is required, except for specifying the role in advance and having the application layer schedule network traffic between the Timing Master and all other nodes at regular intervals. This ensures time synchronization within the network implicitly. The synchronization information is stored in the TX timestamp t tx , the number of hops h, and the TX ID, all of which are transmitted, for example, as part of the packet header (field), as well as a common deterministic hop delay period d, which is stored, for example, locally at each node. CH In particular, the synchronization control unit CONFIG prompts the second data network node 110B to perform the following steps when the second data network node 110B is acting as a subordinate data network node 110S:

[0085] This allows the master clock timestamp t tx Then, when the single-hop data transmission link is defined according to the first embodiment or as shown in FIG. 3A or FIG. 4A, the synchronous data packet SDP is delayed after it is received by the data receiving unit RX, as shown in FIG. 5 (path (a) in FIG. 5). When the single-hop transmission link is defined according to the second embodiment, i.e., as shown in FIG. 3B and FIG. 4B, no delay occurs due to the delay buffer CDB (path (b) in FIG. 5). Because, within a certain delay matching period d ARXis added to the incoming transmission link x by the preceding transmission data network node 110. Next, the slave clock CLK_S of the second data network node 110B or 110S is synchronized under the control of the communication control unit LCU / CONFIG. Therefore, the slave clock CLK_S of the second data network node 110B is calculated based on the number of completed hops h and the common deterministic hop delay period d of the synchronization data packet SDP between the master data network node 110M and the second data network node 110B according to equation (1). CH and synchronized to the master clock time.

[0086] If the second data network node 110B acts as the master data network node 110M, the synchronization control unit CONFIG prompts it to perform the following steps: tx At master clock timestamp t tx The synchronization data packet SDP is transmitted to the subordinate data network node 110S with the master clock timestamp t tx In addition to the number of hops h and the identifier ID_M of the master data network node 110M.

[0087] The present invention also provides a method for initializing a synchronous data network system 10, which includes the following steps, as shown in Figure 7: In step S210, a round trip measurement command RTMR is sent from the communication control unit LCU of the subordinate data network node 110S to the data sending unit TX of the subordinate data network node 110S. In step S220, the data sending unit TX of the subordinate data network node 110S sends a round trip measurement command RTMR to the data sending unit TX of the subordinate data network node 110S. XBB , x BBY, and sends a round-trip signal or a ping signal to the data receiving unit RX of the corresponding additional subordinate data network node 110S via the corresponding direct data transmission link x of the corresponding additional subordinate data network node 110S.

[0088] In this process, in step S230, a timer of the tributary data network node 110S is started upon transmission of a round trip signal by the delay matching unit LMU of the tributary data network node 110S. After the data receiving unit RX of the tributary data network node 110S receives (S240) a returned round trip signal from the corresponding additional tributary data network node 110S via the corresponding direct data transmission link x, in step S250, the timer is stopped by the delay matching unit LMU of the tributary data network node 110S upon receiving the returned round trip signal. In step S260, the round trip delay d RT is read, and in step S270, the intrinsic node delay d SRX_B The round trip delay d RT Adding half of the x to the single-hop data transmission link under test XBB , x BBY The specific hop delay d H_XBB , d H_BBY is calculated for all the single-hop data transmission links x XBB , x BBY After repeating step S280 for all single-hop data transmission links x XBB , x BBY The confirmed hop delay d H_XBB , d H_BBY is saved (S290).

[0089] If during initialization the master data network node 110M specifies a common hop delay from all the confirmed hop delays of all the single-hop data transmission links to be measured, the following additional steps can be performed if necessary: ​​In step S2100, all the single-hop data transmission links x to be measured are identified. XBB , x BBY The confirmed hop delay d H_XBB , d H_BBY is transmitted to the master data network node 110M. In step S2110, the single-hop data transmission links x of all the subordinate data network nodes 110S to be measured are XZZ , x ZZY The confirmed hop delay d H_XZZ , d H_ZZY After the master data network node 110M receives the transmitted hop delay d H_XZZ , d H_ZZY From the common hop delay d CH , but with a given fixed common hop delay d CH is the total transmission hop delay d H_XZZ , d H_ZZY becomes larger than

[0090] 8 illustrates a synchronization method for a synchronous data network system 10 provided in the present invention, which includes at least one master data network node 110M and one subordinate data network node 110S, and includes the following steps: tx , the master clock timestamp t tx In step S320, the master data network node 110M transmits a synchronization data packet SDP having the master clock timestamp t txIn step S330, upon receiving the synchronization data packet SDP, the slave clock CLK_S of the slave data network node 110S calculates 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 110S and the common deterministic hop delay period d according to equation (1). CH and synchronized to the master clock time.

[0091] In accordance with the present invention, a synchronous data network system 10, a master data network node 110M, and a subordinate data network node 110S are provided, which are configured to perform the above-described initialization or synchronization method in accordance with the present invention.

Claims

1. A synchronous data network system (10), comprising: a data network (100) connecting the data network nodes (110) to each other for data exchange via bidirectional direct data transmission links (x) between adjacent data network nodes (110); a node chain of said data network nodes (110) consisting of a first data network node (110A), a second data network node (110B) and a third data network node (110C) in succession, The second data network node (110B) Data transmission link (x ＡＢＢＣ ) from the first data network node (110A) on a first direct data transmission link (x) between the first data network node (110A) and the second data network node (110B), ＡＢ ) and receives the data sent by The received data is transmitted in a transmission mode over a second direct data transmission link (x) between the second data network node (110B) and the third data network node (110C). ＢＣ ) to said third data network node (110C), and Hop delay (d Ｈ＿ＡＢＢ , d Ｈ＿ＢＢＣ ) and a predetermined fixed common hop delay (d ＣＨ ) is equal to the single-hop data transmission link (x) between the first data network node (110A) and the third data network node (110C). ＡＢＢ , x ＢＢＣ 2. A synchronous data network system (10) configured to delay transmission of data over a network.

2. a master data network node (110M) having a master clock (CLK_M); The master data network node (110M) Synchronous data packets (SDPs) are sent as master clock timestamps (t ｔｘ ) to the subordinate data network node (110S), Based on the following formula <1>, the number of completed hops h of the synchronous data packet (SDP) between the master data network node (110M) and the subordinate data network node (110S) and the common hop delay period d ＣＨ 2. The synchronous data network system (10) of claim 1, configured to synchronize the slave clocks (CLK_S) of the slave data network nodes (110S) to a master clock time according to the master clock time. t ｍａｓｔｅｒ =t ｔｘ +d ＣＨ *h 〈1〉

3. The single-hop data transmission link (x ＡＢＢ , x ＢＢＣ ) is the data transmission link (x ＡＢＢ ) and The data transmission link (x ＡＢＢ )but, Starting from the transmitting side of said first data network node (110A), a direct data transmission link (x) between said first data network node (110A) and said second data network node (110B); ＡＢ ) through said second data network node (110B), A synchronous data network system (10) according to claim 1 or 2, characterized in that it terminates at the transmitting side of said second data network node (110B).

4. The single-hop data transmission link (x ＡＢＢ , x ＢＢＣ ) is the data transmission link (x ＢＢＣ ) and The data transmission link (x ＢＢＣ ) starting from the receiving side of said second data network node (110B), A direct data transmission link (x) between the second data network node (110B) and the third data network node (110C) passes through the second data network node (110B). ＢＣ ) via A synchronous data network system (10) according to claim 1 or 2, characterized in that it terminates at the receiving side of said third data network node (110C).

5. The second data network node (110B) a data transmission unit (TX) connected to a direct data transmission link (x) for transmitting data (ODP) to another data network node (110); a data receiving unit (RX) connected to a direct data transmission link (x) for receiving data (IDP) from another data network node (110); The current single-hop data transmission link (x ＡＢＢ , x ＢＢＣ ) stored specific hop delays (d Ｈ＿ＡＢＢ , d Ｈ＿ＢＢＣ ) and a predetermined fixed common hop delay period (d ＣＨ ) and the current single-hop data transmission link (x ＡＢＢ , x ＢＢＣ ) for a specific delay matching period (d ＡＲＸ a delay matching unit (LMU) configured to calculate The specific delay matching period (d ＡＲＸ ), the current single-hop data transmission link (x ＡＢＢ , x ＢＢＣ 5. A synchronous data network system (10) according to claim 1, further comprising a delay buffer (CDB) for delaying the transmission of data packets (RDP_fwd) on the synchronous data network.

6. The delay matching unit (LMU) The single-hop data transmission link (x ＡＢＢ , x ＢＢＣ ) round trip delay (d ＲＴ a timer for measuring the Intrinsic node delay (d ＳＲＸ＿Ｂ ) and the single-hop data transmission link (x) of the second data network node (110B). ＡＢＢ , x ＢＢＣ ) round trip delay (d ＲＴ ) and a predetermined fixed common hop delay (d ＣＨ ) and a memory for storing the Using equation 1, the delay matching period (d ＡＲＸ 6. The synchronous data network system (10) of claim 5, further comprising a calculation unit configured to calculate: d ＡＲＸ =d ＣＨ -d ＲＴ / 2-d ＳＲＸ＿Ｂ 〈2〉

7. the second data network node (110B) comprises a communication control unit (LCU / CONFIG) for controlling initialization and synchronization; The communication control unit (LCU / CONFIG) an initialization control unit (LCU) for controlling the initialization process of the data network node (110); A synchronous data network system (10) according to any one of claims 1 to 6, characterized in that it comprises a synchronization control unit (CONFIG) for controlling the synchronization of the data network nodes (110).

8. The initialization control unit (LCU) As a subordinate data network node (110S) to the second data network node (110B), sending a round trip measurement command (RTMR) from the communication control unit (LC) to the data transmission unit (TX); The data transmission unit (TX) measures the single-hop data transmission link (x ＸＢＢ , x ＢＢＹ a round-trip signal or a ping signal being transmitted via a corresponding direct data transmission link (x) of the corresponding receiving data network node (110) to a data receiving unit (RX) of the corresponding receiving data network node (110); starting a timer by a delay matching unit (LMU) upon transmission of the round trip signal; receiving, by said data receiving unit (RX), said round trip signal transmitted back from a corresponding data network node (110) via a corresponding direct data transmission link (x); stopping the timer upon receipt of the round trip signal transmitted back by the delay matching unit (LMU); The timer returns the round trip delay (d ＲＴ ) and Intrinsic node delay (d ＳＲＸ＿Ｂ ) into the round trip delay (d ＲＴ ) to obtain the single-hop data transmission link (x ＸＢＢ , x ＢＢＹ ) specific hop delay (d Ｈ＿ＸＢＢ , d Ｈ＿ＢＢＹ ) and The above steps are repeated for all the single-hop data transmission links (x ＸＢＢ , x ＢＢＹ ) and All the single-hop data transmission links (x ＸＢＢ , x ＢＢＹ ) confirmed hop delay (d Ｈ＿ＸＢＢ , d Ｈ＿ＢＢＹ 8. The synchronous data network system (10) of claim 7, further comprising:

9. A synchronization control unit (CONFIG) As a subordinate data network node (110S) to the second data network node (110B), From the master data network node (110M) having the master clock (CLK_M), the master clock timestamp t ｔｘ receiving the Synchronous Data Packet (SDP) having: Based on the formula (1), the number of completed hops h of the synchronous data packet (DLP) between the master data network node (110M) and the second data network node (110B) and the common deterministic hop delay period d ＣＨ and synchronizing the slave clock (CLK_S) of the second data network node (110B) to the master clock time in accordance with the master clock time.

10. A synchronization control unit (CONFIG) As a master data network node (110M) to the second data network node (110B), Time t ｔｘ At the master clock timestamp t ｔｘ 8. The synchronous data network system (10) according to claim 7, characterized in that it prompts the execution of a step of transmitting a synchronous data packet (SDP) having the following to a subordinate data network node (110S).

11. The Synchronous Data Packet (SDP) includes a master clock timestamp (t ｔｘ 11. The synchronous data network system (10) according to claim 9 or 10, characterized in that in addition to the number of hops (h) and the identifier (ID_M) of the master data network node (110M), the number of hops (h) and the identifier (ID_M) of the master data network node (110M) are included.

12. A synchronous data network system (10) according to any one of claims 1 to 11, characterized in that it is an avionics system data network for deterministic communication between said data network nodes (110).

13. A method for initializing a synchronous data network system (10), comprising: A step (S210) of transmitting a round trip measurement command (RTMR) from a communication control unit (LC) of a subordinate data network node (110S) to a data transmission unit (TX) of the subordinate data network node (110S); The data transmission unit (TX) of the subordinate data network node (110S) transmits the single-hop data transmission link (x ＸＢＢ , x ＢＢＹ (S220) sending a round-trip signal or a ping signal to a data receiving unit (RX) of a corresponding additional subordinate data network node (110S) via a corresponding direct data transmission link (x) of the additional subordinate data network node (110S); a step (S230) of starting a timer of the subordinate data network node (110S) upon transmission of the round trip signal by the delay matching unit (LMU) of the subordinate data network node (110S); a data receiving unit (RX) of said subordinate data network node (110S) receiving (S240) said round trip signal sent back from a corresponding additional subordinate data network node (110S) via a corresponding direct data transmission link (x); a delay matching unit (LMU) of said subordinate data network node (110S) stopping said timer upon receiving said returned round trip signal (S250); The timer of the subordinate data network node (110S) calculates the round trip delay (d ＲＴ ) (S260); Intrinsic node delay (d ＳＲＸ＿Ｂ ) into the round trip delay (d ＲＴ ) to obtain the single-hop data transmission link (x ＸＢＢ , x ＢＢＹ ) specific hop delay (d Ｈ＿ＸＢＢ , d Ｈ＿ＢＢＹ ) (S270); The above steps are repeated for all single-hop data transmission links (x ＸＢＢ , x ＢＢＹ ) (S280); All the single-hop data transmission links (x ＸＢＢ , x ＢＢＹ ) confirmed hop delay (d Ｈ＿ＸＢＢ , d Ｈ＿ＢＢＹ and (S290) storing the data set information.

14. A synchronization method for a synchronous data network system (10) including at least one master data network node (110M) and a subordinate data network node (110S), comprising: Time t ｔｘ , via the master data network node (110M), the slave data network node (110S) receives a master clock timestamp t ｔｘ transmitting a Synchronous Data Packet (SDP) having: From the master data network node (110M) having a master clock (CLK_M), via the slave data network node (110S), the master clock timestamp t ｔｘ receiving a Synchronous Data Packet (SDP) having: Based on the following formula <1>, the number of completed hops h of the synchronous data packet (SDP) between the master data network node (110M) and the subordinate data network node (110S) and the common deterministic hop delay period d ＣＨ and (S330) synchronizing the slave clock (CLK_S) of the slave data network node (110S) to the master clock time according to the master clock time. t ｍａｓｔｅｒ =t ｔｘ +d ＣＨ *h 〈1〉

15. A synchronous data network system (10) comprising at least one said master data network node (110M) and said subordinate data network node (110S), and configured to implement the method according to claim 13 or 14.

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