Patent Publication Number: US-2022224645-A1

Title: End system for an avionics communication system and associated avionics communication system

Description:
FIELD OF THE INVENTION 
     The present invention relates to an end system for an avionics communication system. 
     The present invention also concerns an avionics communication system associated with this end system. 
     In particular, the invention enables the implementation of a mixed avionics network transmitting frames compliant with the ARINC 664 P7 type protocol and with an IEEE 802 type protocol different to this ARINC 664 P7 protocol. 
     BACKGROUND OF THE INVENTION 
     As is well known, the ARINC 664 standard allows for the implementation of avionics computer networks. Derived from the Ethernet standard, it enables, in particular, the adaptation of this standard to the avionics context and in particular, to avionics constraints. It should be noted that the A664 standard, due to adaptations, is incompatible with the IEEE 802.3 Ethernet standard. 
     The ARINC 664 standard is composed of several parts, such as: a part dedicated to system concepts, a part dedicated to the physical layer, a part dedicated to services and protocol (IP). 
     Among these parts, the part referred to as “P7” and generally referred to as “ARINC 664 P7” or “ARINC 664 Part 7” or “AFDX®” is well known. 
     This P7 part can be used to transmit avionics data between different avionics systems implementing essential aircraft functions, and thus has the highest number of constraints. 
     Thus, an avionics network implemented according to part P7 potentially has a segregated, redundant and deterministic network. In particular, the determinism of this network means that each frame transmitted reaches its destination in a known maximum time. In particular, segregation means that one or more subscribers who do not meet the time constraints of the A664 P7 standard cannot disrupt the proper functioning of the network. 
     In some avionics networks, it is also possible to use one or more protocols from the IEEE 802 family. As is well known, this family particularly includes the Ethernet 802.3 protocol or the IEEE 802.11 Wi-Fi protocol. 
     The A664 P7 standard was created to enable the use of a data network in a critical environment. In particular, it allows for the segregation of data flows with very low granularity, which is not possible with the IEEE 802 family of protocols. 
     In the avionics world, the Ethernet protocol can also be used to transfer data which may be, for example, maintenance data, download data, passenger entertainment data and/or crew service functions relating to different avionics systems. This means that if this data is lost, it can be re-transmitted without creating a safety risk for the aircraft. 
     Typically in an aircraft, the ARINC 664 P7 and IEEE 802 networks are segregated from each other. This segregation is achieved by using different physical means to implement these networks. 
     In particular, this means that to ensure this segregation, these networks use physically different switches and transmission media. 
     It is therefore conceivable that this type of segregation implies at least a doubling of each physical component implementing these networks. This then implies many problems in terms of space, power consumption and weight in a structure hosting these networks, such as an aircraft. 
     In the state of the art, some examples of so-called mixed networks are already known, i.e. networks of both ARINC 664 P7 and IEEE 802 type. 
     Thus, for example, the applicant&#39;s application FR 18 74166 discloses a mixed avionics system implementing mixability of the ARINC 664 P7 and Ethernet protocols with predetermined routing. 
     In particular, such a system comprises switches which are adapted to determine, on receipt of each frame, the protocol of the frame and thus to process this frame in accordance with the determined protocol. 
     The system described in the above document also includes equipment, also known as “End System” in English or “Système d&#39;extrémité” in French. Like switches, end systems must be adapted to handle mixed flows. However, the functioning of these end systems is not always optimal. 
     SUMMARY OF THE INVENTION 
     The present invention is intended to optimise the operation of the end systems of a mixed avionics system. 
     To this end, the invention relates to an end system for an avionics communication system, the avionics communication system also comprising a plurality of switches connected together to form one or more computer networks, the end system being configured to be connected to at least one of the switches to receive and/or transmit digital data in the form of frames through this switch; 
     Each frame having an identification field and being of a first type or a second type, the identification field of each frame defining an identification value, the frames of the first type conforming to a protocol of the ARINC 664 P7 type and the frames of the second type conforming to a protocol of the IEEE 802 type, the set of frames of the first type having the same identification value forming a single flow of the first type and the set of frames of the second type having the same identification value forming a single flow of the second type; 
     The end system being characterised in that it comprises at least one input port capable of receiving frames, and a configuration table comprising, for each identification value, parameters for processing frames that have this identification value; and 
     In that it is able to determine a processing protocol for each frame received via the input port exclusively from the processing parameters corresponding to the identification value of this frame in the configuration table, independently of the type of this frame. 
     In other beneficial aspects of the invention, the end system comprises one or more of the following features, taken in isolation or in any technically possible combination:
         The identification value is a destination address of the frame;   The identification field of each frame corresponds to the MAC DEST field of this frame;   The set of frame identification values of each type and the corresponding processing parameters are statically determined in the configuration table;   For each identification value, the processing parameters include a parameter indicating the need for redundancy management of each frame with has this identification value;   At least one output port capable of transmitting frames of the first type and/or the second type;   The system is configured to transmit each frame of the second type at a timing period predefined by the identification value of this frame;   Each timing period is defined by the processing parameters associated with the corresponding identification value;   The system is configured to transmit each second type frame by filling the available bandwidth after the transmission of the corresponding first type frames.       

     The present invention also relates to an avionics communication system comprising at least two end systems as defined above and at least one switch connected to each of the end systems. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These characteristics and advantages of the invention will become apparent upon reading the following description, given only as a non-limiting example, referring to the attached drawings, in which: 
         FIG. 1  is a schematic view of an aircraft with an ARINC 664 P7 avionics network and an IEEE 802 avionics network; 
         FIG. 2  is a schematic view of a communication system according to the invention, with the communication system implementing the avionics networks in  FIG. 1 ; 
         FIG. 3  is a schematic view of the frames sent by the communication system in  FIG. 2 ; 
         FIG. 4  is a schematic view of an end system that is part of the communication system in  FIG. 2 ; 
         FIG. 5  is a schematic view of the bandwidth distribution implemented by the end system in  FIG. 4 , according to a first embodiment of the invention; and 
         FIG. 6  is a schematic view of the bandwidth distribution implemented by the end system in  FIG. 4 , according to a second embodiment of the invention. 
     
    
    
     In everything that follows, any mention of a norm or standard, in particular an IT standard, refers to the general principles of this norm, which are well known to the person skilled in the field and which are independent of different versions of this norm, unless explicitly stated. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an aircraft  10 , such as a plane. 
     Aircraft  10  comprises a 12 ARINC 664 P7 avionics network and a 14 IEEE 802 avionics network. 
     The 12 avionics network allows sensitive data to be transmitted between different avionics systems. Sensitive data includes any data whose loss or delay in transmission may affect the safety of the aircraft  10 . 
     The 14 avionics network allows less sensitive data to be transmitted compared to the 12 avionics network. Thus, for example, this data corresponds to maintenance data exchanged between the aircraft  10  and the ground and/or functional data exchanged with the crew and/or passenger entertainment data and/or any other type of data. 
     The digital data flowing through the two networks  12  and  14  are respectively in the form of first type frames and second type frames. 
     Thus, the first frame type conforms to the ARINC 664 P7 type protocol and the second frame type conforms to the IEEE 802 type protocol. 
     In particular, “IEEE 802-type protocol” means one of the protocols of the IEEE 802 family of protocols. Such a protocol is, for example, the Ethernet 802.3 protocol or one of the 802.1xxx protocols, i.e. the IEEE 802.11 Wi-Fi protocol, the 802.1Q protocol or the MilStd 1553 protocol. 
     An example of each type of frame is illustrated in  FIG. 3 . In particular, with reference to this figure, the example of a first type frame is designated by the numerical reference “15” and the example of a second type frame is designated by the numerical reference “16”. 
     Each frame transmitted in the corresponding network  12 ,  14  includes an identification field. 
     In the example described, this identification field is included in a header of the frame and forms, for example, a field called “MAC DEST”. In  FIG. 3 , the header is denoted by the reference “MAC HEADER”. 
     As is well known, the MAC DEST field designates the MAC address of the recipient equipment of the corresponding frame. 
     Each identification field takes on an identification value which, in the example described, corresponds to the MAC address of the equipment receiving the corresponding frame. In other words, the identification value defines a virtual link (also called VL) in the case of ARINC 664 P7 type protocol frames. 
     In other embodiments, the identification field is formed by any other field in the frame header, such as the MAC SOURCE field designating the MAC address of the equipment transmitting the corresponding frame. 
     In yet other embodiments, the identification field is formed by at least part of the payload field of the frame. 
     In general, the frame identification field should be understood as any field in the frame that allows the determination of the switching rules for said frame within a given switch, as will be explained later. 
     The set of first type frames with the same identification value form a single first type flow and the set of second type frames with the same identification value form a single second type flow. 
     In other words, each flow of each type is formed by all the frames with the same identification value. Thus, the identification field of each frame also presents an identifier of the flow to which that frame is associated. 
     According to the invention, avionics networks  12  and  14  are implemented by a single physical avionics communication system  20 . 
     An example of such an avionics communication system  20  is shown in  FIG. 2 . 
     Thus, with reference to this figure, this communication system  20  comprises a plurality of switches  22 A, . . . ,  22 N and a plurality of end systems  24 A, . . . ,  24 M. The number of these different components and the way in which they are interconnected may, of course, vary according to the examples. 
     Switches  22 A, . . . ,  22 N are connected to each other by transmission means which also have, for example, a twisted pair cable or any other type of cable allowing bi-directional data transmission or wireless links transmitting digital data via radio waves. 
     Switches  22 A, . . . ,  22 N are, for example, substantially similar to each other. Thus, in the example described, each switch  22 A, . . . ,  22 N is adapted to receive each frame via an input port to transmit it via an output port. For this purpose, upon receipt of each frame, each switch  22 A, . . . ,  22 N is, for example, able to determine the type of this frame and to transmit it to a corresponding output port. According to another embodiment, upon receipt of each frame, each switch  22 A, . . . ,  22 N is adapted to determine the identification value of that frame and to determine the corresponding output port from this value. In this case, each switch  22 A, . . . ,  22 N is, for example, adapted to store a configuration table comprising, for each identification value, switching rules for frames that have this identification value. In all cases, each switch  22 A, . . . ,  22 N is adapted to transmit each frame of the first type in priority to each frame of the second type. 
     According to various embodiments, each switch  22 A, . . . ,  22 N is also adapted to apply at least one filtering operation to each first type frame, and in some examples to each second type frame. This filtering operation may include controlling a timing period of frames with the same identification value, controlling the size of packets transmitted by the frames, controlling the lifetime of frames, etc. 
     Each end system  24 A, . . . ,  24 M, also known as “End System” or simply “equipment”, is integrated in an avionics system and provides communication of this system with networks  12  and  14 . 
     Thus, depending on the avionics system in which it is integrated, each end system  24 A, . . . ,  24 M may be a transmitter and/or receiver of digital data. 
     Furthermore, at least some of the end systems  24 A, . . . ,  24 M may belong only to network  12  or only to network  14 . In this case, such an end system is able to transmit and/or receive digital data only from this network. At least some of the other end systems  24 A, . . . ,  24 M may belong to both network  12  and network  14  insofar as they are able to transmit and/or receive digital data from both networks. 
     Each end system  24 A, . . . ,  24 M is connected to at least one of the switches  22 A, . . .  22 N via transmission means and via at least one port of this switch. The transmission means include, for example, a twisted-pair cable or any other type of cable allowing bi-directional data transmission or wireless links transmitting digital data via radio waves. 
     As with the end systems  24 A, . . . ,  24 M, each transmission medium may belong to only one of the networks  12  and  14 , or to both networks  12  and  14 . This depends, in particular, on the nature of the end system  24 A, . . . ,  24 M which the corresponding transmission means connects to the corresponding network. 
     Within the corresponding 12, 14 network, each end system  24 A, . . . ,  24 M is identified by its MAC address. In particular, in the case of the ARINC 664 P7 type 12 network, several MAC addresses can be associated with the same end system  24 A, . . . ,  24 M. Each of these addresses corresponds to a virtual link leading to this end system  24 A, . . . ,  24 N. 
     In the case of the IEEE 802 14 network, for example, only one MAC address (“unicast” address) is generally associated with each corresponding end system. There are also “multicast” and “broadcast” MAC addresses that an end system must be able to receive. 
     Thus, when the same end system belongs to both networks  12  and  14 , it can be associated with one MAC address (“unicast”) for network  14  and one or more MAC addresses for network  12 . 
     Hereafter, the structure of the end system  24 A will be described in detail with reference to  FIG. 4 . It will be further considered that this end system  24 A belongs to both networks  12  and  14 , and is capable of transmitting frames into these networks and receiving frames from these networks. The structure of the other end systems  24 B, . . . ,  24 M is similar to this one, with obvious adaptations depending on the nature of the system. 
     Thus, with reference to  FIG. 4 , the end system  24 A comprises a plurality of input ports  31 , a plurality of output ports  32 , a configuration table  33  and control means  34 . It should be noted that in this figure, only the external ports, i.e. the ports connecting the system  24 A to the networks  12  and  14 , are shown. Any internal ports or links connecting this  24 A end system to the various components (applications) of the avionics system in which it is integrated are therefore not shown and will not be described in detail below. 
     Each input port  31  is capable of receiving frames of the first type and/or the second type. 
     Each output port  32  is capable of transmitting frames of the first type and/or the second type. 
     Configuration table  33  is used to determine frame processing rules within the end system  24 A. 
     For this purpose, configuration table  33  is stored in a dedicated memory of end system  24 A, and comprises a list of identification values and for each identification value, parameters for processing frames with that identification value. These processing parameters are then defined by each flow that may be transmitted or received by end system  24 A. 
     According to an advantageous embodiment of the invention, the memory of end system  24 A dedicated to the storage of the configuration table is of CAM type. In other words, this memory is implemented using CAM (Content Addressable Memory) technology, which means that it is content addressable. 
     According to this example, the memory of end system  24 A is initialised with the list of identification values. This means, in particular, that each identification value has a memory address referring to a storage field containing the processing parameters corresponding to this identification value. This makes it possible to search for the identification parameters corresponding to a given identification value very quickly, or even almost instantaneously, compared to a traditional search in a list. 
     In one embodiment, the list of identification values is determined statically. This means that this list is determined, for example, at the design stage of the system and cannot be changed during its operation. It is therefore pre-determined processing of frames of each type. 
     In another embodiment, at least some of the identification values in this list are determined dynamically. In other words, these values can be deleted or added during the operation of system  20 . In this case, these identification values relate only to second type flows. It should be noted that when a CAM is used, an address in this memory can also be added or deleted dynamically as a result of adding or deleting an identification value. 
     As for the identification values of the first type of frames, i.e. the identification values of the ARINC 664 P7 flows, these can only be defined statically in order to guarantee the determinism of the network  12 . 
     For each identification value of the flows to be received by the end system  24 A, the processing parameters are of the same nature and are notably independent of the protocol of the frames of the corresponding flow. In other words, for each identification value of the flows intended to be received by end system  24 A, the processing parameters are advantageously composed of the same number of parameters, which are ordered in the same way and independently of the protocol of the corresponding flow. 
     Thus, these flow processing parameters intended to be received by the end system  24 A, include for each identification value at least one identifier of an internal port or an internal transmission link to which each frame received by the system  24 A is to be transmitted. 
     Advantageously, the parameters for processing the flows intended to be received by the end system  24 A also include, for each identification value, a parameter indicating the need for redundancy management of each frame that has this identification value. 
     Advantageously, in a particular example of implementation of the invention, this parameter is “true” for each identification value corresponding to a flow of first type and “false” for each identification value corresponding to a flow of second type. 
     Redundancy management is in accordance with the requirements of the ARINC 664 P7 type protocol. In particular, in a manner known per se, the redundancy management of a frame comprises, upon transmission of this frame by the corresponding end system, the generation of several replicas of this frame and, upon reception by the corresponding end system, the comparison of all the replicas and, as a function of this comparison, the rejection of these replicas or the deletion of at least some of them in order to retain only the original frame. The replicas corresponding to the same frame can, for example, be determined by using a sequential number at the end of each frame. In the example of frames of the first type, this may correspond to the SN field shown in  FIG. 3  in relation to frame  15 . 
     Thus, advantageously according to the invention, the redundancy mechanism is applied to each frame of the first type and is not disturbed by the traffic of the second type frames. 
     Just like the parameters for processing the identification values of the flows intended to be received by the end system  24 A, the parameters for processing the identification values of the flows intended to be transmitted by end system  24 A are of the same nature and are in particular independent of the protocol of the corresponding flow frames. In other words, for each identification value of the flows intended to be sent by end system  24 A, the processing parameters are advantageously composed of the same number of parameters, which are ordered in the same way and independently of the protocol of the corresponding flow. 
     For each flow identification value intended to be transmitted by the end system  24 A, the processing parameters include at least one frame timing period of the corresponding flow and at least one output port  32  of the frames of that flow. 
     The timing period then defines a timing period for the frames of the flow corresponding to a minimum interval of transmission of two consecutive frames of the same flow. 
     For the first type of flow, the timing period is known as the Bandwidth Allocation Gap (BAG). This timing period makes it possible to define an authorised bandwidth for the corresponding flow. 
     In a first embodiment, timing periods are also associated with the second type of flow. In this case, the second type of flows are then said to be “BAGged” insofar as properties similar to those of the first type of flows are associated with these second type flows. In this case, it is therefore also possible to associate a predetermined bandwidth for each flow of the second type. 
     The transmission of frames according to this first embodiment through the same output port  32  is schematically illustrated in  FIG. 5 . 
     In particular, according to the example of this figure, a timing period BAGVLx is determined for a flow of first type and a timing period BAGVLy is determined for a flow of second type. The timing period BAGVLx is shown on the time axis VLx, and the timing period BAGVLy is shown on the time axis VLy. 
     These periods are determined according to the available bandwidth at the corresponding times. 
     Thus, when transmitting the first type frames denoted in  FIG. 5  by “A664P7 REQUEST T0”, . . . , “A664P7 REQUEST T4” and the second type frames denoted in  FIG. 5  by “ETHERNET REQUEST T0”, . . . , “ETHERNET REQUEST T3”, these frames are transmitted according to their timing periods as illustrated on the NETWORK time axis. In addition, the transmission of the first type of frames takes priority over the transmission of the second type of frames, as explained in connection with switches  22 A, . . . ,  22 N. 
     In a second embodiment, predetermined timing periods are not associated with second type flows. In this case, the corresponding values in configuration table  33  may be equal to a predetermined value (e.g. 0); which then means that no particular timing period is associated with the corresponding flow. 
     According to this embodiment, each output port  32  is configured to transmit each second type frame by filling the available bandwidth after transmission of the corresponding first type frames. 
     The transmission of frames according to this second embodiment through the same output port  32  is schematically illustrated in  FIG. 6 . 
     In particular, according to the example of this figure, a timing period BAGVLx is determined for a flow of the first type and is illustrated on the time axis VLx. 
     When transmitting frames of the first type denoted in  FIG. 6  as “A664P7 REQUEST T0”, . . . , “A664P7 REQUEST T4”, these frames are transmitted according to their timing period as illustrated on the NETWORK time axis. As regards the second type of frames denoted by “ETHERNET REQUEST T0”, . . . , “ETHERNET REQUEST T3”, these are transmitted in the “gaps” formed between the transmissions of the frames by “A664P7 REQUEST T0”, . . . , “A664P7 REQUEST T4”, as can also be seen on the NETWORK time axis. Here, as in the previous case, frames of the first type are transmitted with priority over frames of the second type. 
     In a particular embodiment of the invention, only the parameters for processing the identification values of the flows to be received by the end system  24 A are stored in the configuration table  33 , together with these identification values. As for the processing parameters of the flows to be issued by the end system  24 A, these are stored in a separate table or in any other available means. 
     The control means  34  controls the operation of each input port  31  and output port  32  and is, for example, in the form of a central unit connected to each of these ports, as shown in  FIG. 4 . 
     In another embodiment, the control and switching means  34  are distributed at least partially between the ports  31 ,  32  and thus allow local control of the operation of each of these ports. 
     Control means  34  also enables frames within end system  24 A to be switched between each input port  31  and an internal port or link, and between such an internal port or link and an output port  32 , in accordance with the corresponding flow processing parameters in the configuration table  33 , as explained above. 
     Control means  34  also allows the implementation of redundancy management mechanisms as explained above. 
     It is therefore clear that the present invention has a number of advantages. 
     First of all, the invention allows the implementation of mixability of ARINC 664 P7 and IEEE 802 type networks using the same physical components, i.e. the same transmission means, the same switches and the same input and output ports. 
     This then allows for a considerable reduction in the size and weight of networks  12  and  14  on board aircraft  10 . 
     Finally, the end systems are configured to process frames independently of their type, i.e. independently of the protocol of these frames. The operation of each end system can thus be substantially identical for each frame so that there is no need to distinguish between frames of different protocols. This then allows the operation of the end systems to be optimised.