Method for monitoring a Half Duplex Ethernet network and associated Half Duplex Ethernet network

Abstract

Method for monitoring a Half Duplex Ethernet network and associated Half Duplex Ethernet network. The present invention relates to a method for monitoring a Half Duplex Ethernet network comprising a plurality of nodes and exhibiting a PLCA operating mode and a CSMA / CD operating mode, each node being defined by an identifier. The method comprises the following steps implemented by each node: - retrieval (110) of an internal state of the node describing the network operating mode; - transmission (120) of the internal state to all other nodes; - analysis (130) of the received external states corresponding to the internal states transmitted by other nodes; - based on this analysis, reconfiguration (140) of the node or maintenance of its current configuration. Figure for the abstract: Figure 2

Description

Title of the invention: Method for monitoring a Half Duplex Ethernet network and associated Half Duplex Ethernet network

[0001] The present invention relates to a method for monitoring a network of type Ethernet Half Duplex. The present invention also relates to such an Ethernet Half Duplex network.

[0002] In particular, the Half Duplex Ethernet network according to the invention conforms to one of the following standards: 10BASE-T1S, 100BASE-T1S, 10BASE-T1L, 100BASE-T1L. These standards conform to the IEEE STD 802.3cg type standard.

[0003] Networks of this type, as is known per se, allow the transmission of data from, for example, a plurality of sensors to a central switch. This type of network is a Half Duplex network, insofar as it allows the transmission of frames in both directions between the nodes constituting this network on the same pair of conductors.

[0004] In addition, in a particular operating mode, this type of network implements a collision management technique optimized to use the maximum of the bandwidth available for exchanges between different nodes of the network.

[0005] This mode of operation is known as PLCA (from the English "Physical Layer Collision Avoidance") and is based mainly on the presence of a master node on the network which periodically sends a synchronization signal called a BEACON.

[0006] This synchronization signal allows other nodes to synchronize and determine their own frame transmission opportunities in the network.

[0007] The absence of the synchronization signal on the network, due for example to a failure of the master node called Master, forces the different nodes of the network to reconfigure the collision management mode by switching from PLCA operating mode to a degraded operating mode called CSMA / CD (from the English "Carrier Sense Multiple Access / Collision Detection").

[0008] Switching to such a mode results in a significant decrease in network performance. Indeed, when the network is in this degraded operating mode, each node wishing to transmit a frame on the network first checks if another node is already transmitting frames. In such a case, the first node will wait a random amount of time before performing this check again.

[0009] In certain fields, and in particular in the avionics field, the aforementioned type of network presents an interesting alternative to the networks currently used.

[0010] For example, in the avionics field, the use of ARINC 429 type networks is known for connecting sensors to a centralized switch. However, the type of network conforming to this standard has a very low data rate, typically around 100 Kbit / s, and is only unidirectional.

[0011] On the contrary, for example the 10BASE-T1S type network has a throughput of 10 Mbit / s and the 100BASE-T1S type network has a throughput of 100 Mbit / s.

[0012] Furthermore, a half-duplex network that allows frames to be transmitted in both directions using the same pair of conductors would reduce the required cabling. Indeed, for existing networks, a pair of conductors is necessary to ensure frame transmission in each direction.

[0013] However, replacing existing networks with this type of network presents a number of difficulties.

[0014] In particular, when the network, for example of type 10BASE-T1S, enters its degraded operating mode, the frame transmission time can no longer be bounded.

[0015] This makes the network of this type non-deterministic. The use of non-deterministic networks is problematic in certain fields, particularly in avionics.

[0016] The present invention aims to solve this problem and to make the Ethernet Half Duplex type network (such as 10BASE-T1S, 100BASE-T1S, 10BASE-T1L, 100BASET-1L) deterministic.

[0017] This will then allow its use in many fields, particularly in the avionics field.

[0018] To this end, the invention relates to a method for monitoring an Ethernet Half Duplex network comprising a plurality of nodes and having a PLCA operating mode and a CSMA / CD operating mode, each node being defined by an identifier.

[0019] In PLCA operating mode, a master node sends a synchronization signal to all other nodes for the transmission of their frames.

[0020] In CSMA / CD operating mode, all nodes transmit their frames at random time intervals.

[0021] The process comprises the following steps implemented by each node:

[0022] - retrieval of an internal state of the node describing the operating mode of the network ;

[0023] - transmission of the internal state to all other nodes;

[0024] - analysis of received external states corresponding to internal states transmitted by other nodes;

[0025] - depending on this analysis, reconfiguration of the node or maintenance of its current configuration.

[0026] According to other advantageous aspects of the invention, the method comprises one or more of the following features taken individually or in all technically possible combinations:

[0027] - each internal state indicates the operating mode of the network as seen by the node corresponding;

[0028] - each internal state further indicates whether the corresponding node receives or transmits a synchronization signal;

[0029] - the internal state transmission step includes the integration of this internal state in each frame emitted by the corresponding node;

[0030] - the reconfiguration step of each node includes a deactivation of that node or a shift in its identifier;

[0031] - the identifier offset includes:

[0032] - the assignment of a new identifier chosen according to the maximum number of nodes in the network when the corresponding node is the master node;

[0033] - reducing the identifier from "1" for all other cases;

[0034] - the step of analyzing the received external states includes a validation sub-step including the selection of a valid state from among all the states received;

[0035] - the analysis step includes an analysis of at least three external states resulting from different knots;

[0036] - the validation substep includes the comparison of the received external states and the selection of the valid state corresponding to a common state of a majority of the received external states;

[0037] - the valid state indicates:

[0038] - the PLCA operating mode, the current configuration of the corresponding node is maintained;

[0039] - the CSMA / CD operating mode, the corresponding node is reconfigured by a shift in its identifier;

[0040] - none of these operating modes, the corresponding node is reconfigured by a deactivation of this node;

[0041] - the analysis step includes a substep of activating the mode of CSMA / CD operation when the corresponding node does not receive any frames in a first time interval;

[0042] - following the activation of the CSMA / CD operating mode, the step of Reconfiguration includes shifting the identifier of the corresponding node when that node receives at least one frame in a second time interval and disabling the node otherwise.

[0043] The invention also relates to an Ethernet Half Duplex type network comprising a plurality of nodes and having a PLCA operating mode and a CSMA / CD operating mode, each node being defined by an identifier;

[0044] - in PLCA operating mode, a master node being capable of sending to all other nodes receive a synchronization signal for the transmission of their frames;

[0045] - in CSMA / CD operating mode, all nodes being capable of transmit their frames at random time intervals;

[0046] each node being configured to implement the process as defined above.

[0047] The invention will become clearer upon reading the following description, given solely by way of non-limiting example and with reference to the drawings in which: - [Fig.1] [Fig.1] is a schematic view of an Ethernet Half Duplex type network according to the invention, the network comprising in particular a plurality of nodes; - [Fig.2] [Fig.2] is a flowchart of a network monitoring process of [Fig.1]; - [Fig.3] [Fig.4] [Fig.5] [Fig.6] [Fig.7] Figures 3 to 7 are different illustrations of the implementation of the process of [Fig.2].

[0048] Fig. 1 illustrates a network 10 according to the invention.

[0049] This network 10 is a Half Duplex Ethernet network that conforms to one of the following standards: 10BASE-T1S, 100BASE-T1S, 10BASE-T1L, or 100BASE-T1L. Generally, such a standard is defined in the IEEE STD 802.3cg type standard. "Type X standard" means the current version of the X standard, or any later or earlier version, provided that this version enables the implementation of the features described in relation to that standard below.

[0050] As illustrated in [Fig.1], the network 10 comprises a plurality of nodes 12-0, ... 12-N which are connected by a cable 13. The cable 13 advantageously features a cable with a differential pair, for example a twisted pair cable.

[0051] Each of the nodes 12-0, ... 12-N is integrated into a device capable of generating digital data for sending to other devices via network 10 and / or receiving digital data from these devices. The digital data is transferred via network 10 in the form of frames.

[0052] In particular, according to one embodiment of the invention, the network 10 is usable in the avionics field, for example the network 10 is carried on board an aircraft.

[0053] An aircraft is understood to mean any flying machine which is pilotable at least partially manually and / or at least partially automatically.

[0054] According to one embodiment, at least some of the devices integrating the nodes 12-0, ... 12-N have avionics sensors 14 and a device integrating at least one of these nodes has a switch 15. Such a switch 15 is configured to transmit data generated by the sensors to a centralized computer.

[0055] According to this example, the data generated by the sensors 14 present, for example, measurement data which are then transmitted to the central computer via the network 10 and in particular the switch 15.

[0056] Thus, in the example of the main figure, node 12-0 is integrated into such a switch 15 and the other nodes 12-1 to 12-N are integrated into the sensors 14.

[0057] Furthermore, node 12-0 is also capable of transmitting data to other nodes. This data includes, for example, configuration data for the corresponding sensors 14.

[0058] In a manner known per se, each node 12-0, ... 12-N has a physical interface often implemented by a component called PHY. This physical interface PHY includes, in particular, an internal register storing various operating parameters of the node.

[0059] Furthermore, each node 12-0, ... 12-N is associated with a unique identifier in the network 10. For example, the identifiers of nodes 12-0, ... 12-N correspond to the number of the node assigned within the network and ranging from 0 to N.

[0060] The node identifiers can be changed, as will be described in more detail later.

[0061] In a manner known per se, the network 10 has two modes of operation.

[0062] In a first mode of operation, also called PLCA mode of operation, all frame exchanges in the network 10 are controlled by a synchronization signal transmitted to all nodes by the master node.

[0063] This master node generally has the identifier "0", which distinguishes it from the other nodes in the network. This master node is then configured to periodically send a synchronization signal, also called a beacon. All other nodes are able to receive this synchronization signal and transmit their frames in a predetermined time slot for the corresponding node. This time slot is determined locally by the corresponding node using the synchronization signal. The master node is also configured to act like the other nodes; that is, it is also configured to transmit frames in a predetermined time slot.

[0064] When the corresponding node has no frame to send in its slot, this slot remains empty and no frame is sent into the network during this slot.

[0065] Advantageously, each slot can have a variable duration. For example, each slot can correspond to a duration during which the node can begin transmitting. Each slot therefore has a minimum duration corresponding to the absence of a frame, but this duration can extend to the duration of the frame to be transmitted in the presence of such a frame. In such a case, the next transmitting node will only begin transmitting at the end of the frame transmission by the first node; that is, the next transmitting node will only begin transmitting after the detection of a "silence" in the network.

[0066] The second operating mode of the network 10, also known by the abbreviation CSMA / CD operating mode, is triggered in the network when no synchronization signal is received by the nodes after a cycle, that is, after all nodes have had their turn to transmit. In such a case, each node is able to send its frames at random time intervals to avoid collisions. In particular, when a node tries to send a frame while another node is sending another frame at the same time, the first node will wait a random amount of time before trying to send its frame again.

[0067] According to the invention, each node is further configured to implement a monitoring method according to the invention which allows the network to be reconfigured when it switches to CSMA / CD operating mode, in order to return to PLCA operating mode. This method is, for example, implemented periodically in network 10. In other words, steps 110 to 140 described below can be repeated at predetermined intervals.

[0068] This process will henceforth be explained with reference to [Fig.2] showing an organizational chart of its steps.

[0069] Initially, it is assumed that the network 10 operates according to the PLCA operating mode and the set of nodes 12-0, ..., 12-N are capable of sending and receiving frames.

[0070] It is further considered that the steps described below are carried out by each of the nodes 12-0, ..., 12-N. Thus, these steps will be described with reference to a single node (for example, node 12-1) knowing that all the other nodes are capable of implementing the same steps.

[0071] During an initial step 110, the node 12-1 retrieves an internal state allowing the current operating mode of the network 10 to be described from the point of view of this node.

[0072] In particular, this internal state indicates the network operating mode, either PLCA operating mode or CSMA / CD operating mode. This internal state also indicates whether this node receives or transmits a synchronization signal.

[0073] More specifically, the internal state can indicate the PLCA operating mode and the fact that this node is transmitting a synchronization signal. In other words, this internal state indicates that the corresponding node is the master node in network 10.

[0074] According to another example, this internal state may indicate that the network is in PLCA operating mode and the corresponding node receives a synchronization signal. In such a case, the corresponding node is a slave node which then receives a synchronization signal from a master node.

[0075] The internal state can also indicate the network operating mode If node 10 is in CSMA / CD mode and the corresponding node is not receiving any signaling signal, this corresponds to normal operation of the node in this CSMA / CD operating mode of network 10. In another example, the internal state of the node may indicate that network 10 is in CSMA / CD operating mode, while the corresponding node is receiving or transmitting a synchronization signal. This latter state indicates a network malfunction, which will then be addressed as explained in the following steps of the procedure.

[0076] Advantageously, the internal state of the node is kept in its internal register.

[0077] Recovering such a state therefore includes recovering that state from this internal register of node 12-1.

[0078] During the next step 120, node 12-1 transmits its internal state to all other nodes 12-0, 12-2 to 12-N.

[0079] To do this, node 12-1 integrates its identifier and internal state into each frame emitted by this node in network 10.

[0080] To do this, different techniques are possible.

[0081] According to a first technique illustrated in [Fig. 3], node 12-1 integrates additional data D into a header of each frame. This header corresponds, for example, to the MAC HEADER type header. This additional data D can be integrated more specifically into the field indicating the origin of the frame, called the MAC Source field.

[0082] According to a second technique illustrated in [Fig.4], the additional data D is integrated into the payload of the corresponding frame.

[0083] This payload is known by the English abbreviation Payload.

[0084] According to yet another technique (not illustrated), the additional data D can be integrated into a field independent of the useful application data field Payload. This then implies a reduction in the maximum size of the Payload field.

[0085] In the following step 130, node 12-1 analyzes external states received from other nodes in the network 10 or, if necessary, when these external states have not been received. In particular, by external states, we mean the internal states determined by the other nodes in the network and then transmitted to the corresponding node using the frames emitted by these nodes.

[0086] Analysis step 130 determines whether it is necessary to reconfigure node 12-1 or to maintain its current configuration during step 140, in order to restore the PLCA operating mode of network 10 if necessary.

[0087] Various examples of implementing these steps 130 and 140 are possible. Furthermore, as will be explained later, it is necessary in some cases to implement these steps 130 and 140 several times in order to achieve the PLCA operating mode of network 10.

[0088] An example of a possible implementation of these steps is illustrated in [Fig.5].

[0089] With reference to [Fig. 5], the analysis step 130 comprises a first substep 131 during which node 12-1 waits for the reception of external states from the other nodes. When no external state, i.e., no frame, is received from the other nodes after a first time interval, node 12-1 implements substep 132 during which it forces a switch to CSMA / CD operating mode. Then, node 12-1 again waits for the reception of external states, i.e., frames from the other nodes, during substep 133.

[0090] When, after a second time interval, which is for example equal to the first time interval, node 12-1 still does not receive a frame from the other nodes, it is considered to be faulty and should then be deactivated during step 140. In [Fig. 5], the deactivation of the node then corresponds to the action designated by reference 141. When, on the other hand, node 12-1 receives frames from the other nodes, the node implements a validation substep 134 of the received external statuses. This validation substep 134 will be explained in more detail later.

[0091] When, at the end of step 134, the network status indicating the CSMA / CD operating mode is considered invalid, the node is again considered to be faulty and is then deactivated during step 140 by action 141.

[0092] When, on the contrary, the status indicating the operating mode of the CSMA / CD network is considered valid during step 134, it is considered that the network 10, and in particular the corresponding nodes 12-0 to 12-N, must be reconfigured during step 140 to restore the PLCA operating mode.

[0093] With reference to [Fig.5], this action is then noted by reference 142 and will be explained in more detail later.

[0094] When, during substep 131, node 12-1 receives frames from other nodes, i.e., external states, it implements substep 134 of validating the PLCA status of network 10.

[0095] When this status is considered valid at the end of substep 134, it is considered that network 10, and in particular node 12-1, is functioning normally In PLCA operating mode and during step 140, the current network configuration is maintained.

[0096] With reference to [Fig.5], this action of maintaining the current network configuration corresponds to reference 143.

[0097] When, on the contrary, after the first implementation of the validation step 134, the state indicating the PLCA operating mode of the network 10 is considered invalid, the node 12-1 implements the validation step 134 again, during which it checks this time the validity of the state indicating the CSMA / CD operating mode.

[0098] When, at the end of this second implementation of substep 134, the state indicating the CSMA / CD operating mode is considered valid, it is considered that network 10 and in particular node 12-1 must be reconfigured during step 140 to restore the PLCA operating mode of network 10.

[0099] To do this, node 12-1 implements action 142 during step 140, which will be explained in detail later.

[0100] When, on the contrary, at the end of the second implementation of the validation substep 134, the state indicating the CSMA / CD operating mode is considered invalid, it is considered that the node 12-1 is faulty and must be deactivated during step 140. Thus, during step 140, action 141 including the deactivation of the node is then implemented.

[0101] Fig. 6 illustrates an example of the implementation of substep 134 of validation of external states received by the corresponding node 12-1.

[0102] In general, the validation substep 134 includes comparing the external states received from different nodes and selecting the valid state corresponding to a common state according to a majority of the external states received.

[0103] Thus, according to the example in [Fig.6], substep 134 includes the verification of three conditions.

[0104] The first condition (Condition 1 on [Fig.6]) is satisfied when node 12-1 receives two external statuses from two different nodes.

[0105] When this is not the case, node 12-1 waits until it receives external statuses from two different nodes.

[0106] When two statuses from two different nodes are received, node 12-1 checks the second condition (Condition 2 on [Fig.6]) which consists of comparing the statuses received.

[0107] When the statuses are identical, node 12-1 concludes that this status is valid. Conversely, when the second condition is not met, i.e., the statuses received from the two different nodes are not identical, node 12-1 implements the third condition (Condition 3 in [Fig. 6]) in which it verifies if it has received an external status from a node other than the first two nodes. When this is not the case, node 12-1 waits for such a status from a third node other than the first two nodes.

[0108] When this is the case, the 12-1 node selects the valid state corresponding to the common state according to the majority of external statuses received. In other words, in such a case, the 12-1 node decides the valid status based on the majority.

[0109] Of course, other methods of validating received states are also possible. For example, it is possible to perform a double check of the states received from the same node.

[0110] Figure 7 illustrates the implementation of action 142 carried out during step 140.

[0111] In particular, this action 142 includes shifting the node identifier in order to restore the PLCA operating mode of network 10.

[0112] This offset includes assigning a new identifier determined according to the maximum number of nodes in the network when the corresponding node is the master node. In the case of other nodes, the offset includes reducing the identifier of that node by one.

[0113] In its part A, [Fig.7] illustrates the normal operation of the network 10 according to the PLCA operating mode for nodes with identifiers from 0 to N. Among these nodes, the node with identifier 0 corresponds to the master node which is able to send a synchronization signal to the other nodes.

[0114] In part B, [Fig. 7] illustrates the case where the node with identifier 0 needs to be reconfigured and a new master node needs to be selected. For this purpose, and as illustrated in part C of [Fig. 7], the previous master node receives the identifier corresponding, for example, to the highest identifier of the nodes in the network and thus becomes a slave node. In such a case, the identifiers of all other nodes are reduced by one so that the previous node with identifier number 1 becomes the node with identifier 0. Consequently, this node becomes the new master node.

[0115] The other nodes, that is to say the previous nodes having identifiers ranging from 2 to N, remain the slave nodes but change their identifiers which now range from 1 to N-1.

[0116] When, after a first shift of the identifiers, there is no node with the identifier 0, the shift operation is carried out again until such a node with the identifier 0 is obtained. This new shift operation is carried out during a new implementation of step 140 and action 142, which are then carried out following a new implementation of analysis step 130.

[0117] Thus, network 10 can operate again according to PLCA operating mode. In such a case, the new master node receives and transmits the corresponding synchronization signal.

[0118] It is therefore understood that the present invention has a number of advantages.

[0119] In particular, the invention firstly enables the reliable detection of a network failure. This detection is considered reliable because it results from the redundancy of different states originating from different nodes. This makes the probability of a false detection practically negligible. Secondly, the invention enables the network to be reconfigured to maintain and find the PLCA mode, which is then the desired operating mode.

[0120] The invention also implements a technique for verifying transmitted external states in order to protect the integrity of the network.

[0121] During network reconfiguration, the invention makes it possible to disable a malfunctioning node to prevent any anomaly on the network caused by this node.

[0122] Finally, the invention also allows for a shifting of the node identifiers across the entire network to enable the fastest possible recovery of PLCA operating mode. This operation allows the shifting to be repeated several times in the event of multiple failures. This multiplicity of reconfiguration possibilities makes the network more reliable in an avionics context since the probability of having a system with multiple similar failures is low and decreases with the number of failures.

[0123] The network according to the invention can thus be used effectively, particularly in the avionics field, to replace existing networks, for example networks according to the ARINC 429 standard.

Claims

Demands

1. A method for monitoring a Half Duplex Ethernet network comprising a plurality of nodes (12-0, ..., 12-N) and having a PLCA operating mode and a CSMA / CD operating mode, each node (12-0, ..., 12-N) being defined by an identifier; in the PLCA operating mode, a master node (12-0) sending a synchronization signal to all other nodes (12-1, ..., 12-N) for the transmission of their frames; in the CSMA / CD operating mode, all nodes (12-0, ..., 12-N) transmitting their frames at random time intervals; the method comprising the following steps implemented by each node (12-0, ..., 12-N): - retrieval (110) of an internal state of the node (12-0, ..., 12-N) describing the operating mode of the network; - transmission (120) of the internal state to all other nodes (12-0, ..., 12-N); - analysis (130) of the received external states corresponding to the internal states transmitted by other nodes; - based on this analysis, reconfiguration (140) of the node (12-0, ..., 12-N) or maintenance of its current configuration; the transmission step (120) of the internal state including the integration of this internal state into each frame emitted by the corresponding node (12-0, ..., 12-N).

2. A method according to claim 1, wherein each internal state indicates the operating mode of the network as seen by the corresponding node (12-0, ..., 12-N).

3. Method according to claim 2, wherein each internal state further indicates whether the corresponding node (12-0, ..., 12-N) receives or transmits a synchronization signal.

4. A method according to any one of the preceding claims, wherein the reconfiguration step (140) of each node (12-0, ..., 12-N) includes a deactivation (141) of that node or a shift (142) of its identifier.

5. A method according to claim 4, wherein the offset (142) of the identifier comprises: - the assignment of a new identifier chosen according to the maximum number of nodes (12-0, ..12-N) in the network when the corresponding node (12-0, ..., 12-N) is the master node; - the reduction of the identifier by "1" for all other cases.

6. A method according to any one of the preceding claims, wherein the analysis step (130) of the received external states includes a validation substep (134) comprising the selection of a valid state from among the set of received states.

7. A method according to claim 6, wherein: - the analysis step (130) comprises an analysis of at least three external states from different nodes (12-0, ..., 12-N); - the validation substep (134) comprises the comparison of the received external states and the selection of the valid state corresponding to a common state of a majority of the received external states.

8. A method according to claim 6 or 7, wherein when the valid state indicates: - PLCA operating mode, the current configuration of the corresponding node (12-0, ..., 12-N) is maintained; - CSMA / CD operating mode, the corresponding node (12-0, ..., 12-N) is reconfigured by shifting its identifier; - neither of these operating modes, the corresponding node (12-0, ..., 12-N) is reconfigured by disabling this node (12-0, ..., 12-N).

9. A method according to any one of the preceding claims, wherein the analysis step (130) includes a substep (132) of activating the CSMA / CD operating mode when the corresponding node (12-0, ..., 12-N) does not receive any frames in a first time interval.

10. A method according to claim 9, wherein following activation of the CSMA / CD operating mode, the reconfiguration step (140) includes a shift (142) of the identifier of the corresponding node (12-0, ..., 12-N) when this node (12-0, ..., 12-N) receives at least one frame in a second time interval and a deactivation (142) of the node (12-0, ..., 12-N) otherwise.

11. A network (10) of the Ethernet Half Duplex type comprising a plurality of nodes (12-0, ..., 12-N) and having a PLCA operating mode and a CSMA / CD operating mode, each node (12-0, ..., 12-N) being defined by an identifier; In PLCA operating mode, a master node (12-0) is capable of sending a signal to all other nodes (12-1, 12-N). synchronization signal for transmitting their frames; in CSMA / CD operating mode, all of the nodes (12-0, ..., 12-N) being able to transmit their frames at random time intervals; each node (12-0, ..., 12-N) being configured to implement the method according to any one of the preceding claims.

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