Patent Application
20160285699
The present application claims priority to French Patent Application Number 15 52568, filed Mar. 26, 2015, the disclosure of which is entirely incorporated by reference.
The technology herein relates to the field of communication networks and more particularly to communication networks installed in aircraft.
Aircraft generally comprise one or more onboard communication networks provided to allow communications between onboard equipment, for example onboard computers. In order to meet the regulatory requirements regarding certification of aircraft, an onboard communication network must allow a deterministic transmission of data between the different equipment subscribed to this communication network. The ARINC 664 part 7 standard defines a deterministic onboard avionic communication network, based on a full-duplex Ethernet technology. Such a network can for example correspond to an AFDX® communication network. In a network conforming with the ARINC 664 part 7 standard, each item of equipment is connected to a switch of the network and the communications between the different equipment use virtual links predefined during the design of the network. A virtual link is defined between an item of transmitting equipment and one or more items of receiving equipment, via one or more switches of the network. Each virtual link uses a determined path in the network. A bandwidth is allocated to each virtual link and the routing of the different virtual links of the network is carried out in such a way that the total of the bandwidths allocated to the virtual links using a same physical link does not exceed the bandwidth supported by said physical link. This makes it possible to guarantee the determinism of the network. However, a few constraints result from this, in particular with regard to the configuration management of the network. All of the communications between equipment must be defined in advance, by the definition of the virtual links, in order to allow a configuration of the switches. All communications between the equipment therefore must be defined very early in the process of development of the systems installed in the aircraft. As a result, the configuration of the switches of the network and the configuration of each switch must be downloaded into respective switch before it is used. This configuration must be consistent with the subscribed equipment actually connected to the network. Moreover, when a physical link or a switch of the network is unavailable, the different virtual links passing through that physical link or that switch are unavailable.
The technology herein seeks to provide a solution to the above-identified problems. It relates to a communication network comprising:
a set of links each supporting a specified bandwidth;
a set of subscribers; and
at least one communication node comprising a set of communication ports, these communication ports being connected to links of the set of links.
This network is noteworthy in that:
each one of the set of subscribers is associated with an authorized maximum bandwidth for transmission on the network, in such a way that the total of the authorized maximum bandwidths corresponding to respective subscriber is less than or equal to said authorized maximum bandwidth associated with respective subscriber,
said at least one communication node comprises a processing unit and a memory and the processing unit is configured for, when a data frame is received on one of the communication ports of the communication node:
checking if the memory contains an identifier associated with that data frame; and
if the memory does not contain an identifier associated with that data frame:
sending that data frame to all of the other communication ports of the communication node; and
storing the identifier of the data frame in the memory.
Thus, said at least one communication node distributes the received data frame to all of the other ports. This makes it possible to distribute the frame to all of the destination subscribers, without a configuration of the communication node or nodes of the network. Moreover, by virtue of the identifier associated with a data frame, if the communication node in question receives a data frame several times because of the distribution of said data frame in the network by several communication nodes, the communication node does not retransmit the data frame. This makes it possible to avoid saturation of the communication network by guaranteeing that a same data frame, to which a specified identifier corresponds, can only be transmitted once by a communication port of a communication node. Moreover, given that the total of the authorized maximum bandwidths associated with each of the subscribers is less than or equal to the specified bandwidth supported by each of the links, the data traffic corresponding to data frames transmitted by the different subscribers does not risk saturating the communication network. The communication network therefore makes it possible to route a data frame transmitted by a subscriber, to the destination subscriber (or subscribers), without risking saturation of the network. Moreover, this network does not necessitate a configuration of virtual links in communication nodes of the network, which makes it possible to facilitate modifications of the subscribers of the network. For example, it is possible to modify easily the list of the destination subscribers of a data frame transmitted by a subscriber: such a modification only necessitates a parameterization of the transmitting subscriber and/or of the destination subscriber or subscribers.
Advantageously, the links of the set of links are arranged in pairs in order to form a network of the full-duplex type.
According to one example embodiment, the subscribers of the set of subscribers are configured for communicating on the network according to a communication protocol compatible with the ARINC 664 part 7 standard. Advantageously, the identifier associated with a data frame corresponds to a virtual link identifier and a sequence number of the frame.
According to another example embodiment, the set of subscribers are configured for communicating on the network according to a communication protocol compatible with the Ethernet standard. Advantageously, the identifier associated with a data frame corresponds to an identifier of the transmitting subscriber and a frame number generated by that subscriber.
In a particular example embodiment, the communication network comprises at least four communication nodes, each communication node comprising four communication ports, these communication nodes being arranged according to a matrix topology.
Advantageously, said at least one communication node is integrated in one of the set of subscribers. This makes it possible to simplify the communication network, as the communication network does not need specific equipment for implementing the functions of a communication node. The communication network thus comprises only subscribers and a set of links between these subscribers.
The technology herein also relates to a communication node of a communication network, this network comprising a set of links each supporting a specified bandwidth, the network further comprising a set of subscribers, with each of which is associated an authorized maximum bandwidth for transmission on the network, in such a way that the total of authorized maximum bandwidths corresponding to respective subscriber is less than or equal to the authorized maximum bandwidth associated with respective subscriber, the communication node comprising a set of communication ports, these communication ports being provided for being connected to links of the network.
The communication node comprises a processing unit and a memory and the processing unit is configured for, when receiving a data frame on one of the communication ports of the communication node:
checking if the memory contains an identifier associated with that data frame;
if the memory does not contain an identifier associated with that data frame:
sending that data frame to all of the other communication ports of the communication node; and
storing, in the memory, the identifier associated with the data frame.
Advantageously, the communication node comprises a transmission queue associated with a communication port. Such a queue makes it possible to store data frames received by the communication node, before they are retransmitted, in order to avoid data collisions on the communication links.
The communication node further comprises:
a reception queue associated with a communication port; and
a traffic regulator configured for reading data in the reception queue and for sending these data to the processing unit, whilst limiting the reading and sending of the data in terms of an authorized maximum bandwidth for that communication port.
When this communication port is connected to a subscriber, this makes it possible to limit the data traffic coming from the subscriber and retransmitted by the communication node on the network, in order to protect against saturation of the communication network. The authorized maximum bandwidth for this communication port is then advantageously chosen to be equal to the authorized maximum bandwidth for transmission on the network associated with that subscriber.
The technology herein also relates to an aircraft comprising a communication network such as mentioned above.
These and further aspects of the exemplary implementations will be better understood on reading the following description and on examination of the appended figures.
The communication network 20 shown in
Each subscriber comprises a communication port connected, by a communication link 14, to a communication port of one of the communication nodes. Each communication node comprises several communication ports, for example 4 communication ports as shown in
As shown in
During operation, the data flowing on the different links 14 of the communication network 20 correspond to data frames. A data frame is transmitted, by a subscriber of the network, to one or to several other subscribers of the network. When a communication node 10 receives a data frame on a communication port, for example the port P1, this port transmits the data corresponding to the received data frame to the processing unit 16 by means of the link 15a. The processing unit analyzes the data received and retrieves an identifier associated with the data frame. The processing unit then checks if this identifier is already recorded in the memory M. If the memory does not contain this identifier, then the processing unit sends the data corresponding to the received data frame to the queues Fe2, Fe3 and Fe4 associated with the other communication ports P2, P3 and P4, respectively by the links 18b, 18c and 18d. The data frame is then retransmitted by each of the other communication ports P2, P3 and P4. Moreover, the processing unit 16 records, in the memory M, the identifier associated with the data frame. Thus, the communication node 10 retransmits the received data frame only if the identifier associated with that data frame was not already stored in its memory M, namely, if the data frame had not yet been received by that communication node. On the other hand, if the data frame has already been received by the communication node, then its identifier is already recorded in the memory M and consequently the processing unit 16 does not send the data corresponding to this data frame to the transmission queues Fe2, Fe3 and Fe4. Thus, the data frame is not retransmitted by communication ports P1, P2 or P3. This makes it possible to avoid sending a same data frame several times on a same link of the communication network, which prevents the saturation of the bandwidth supported by said link. The use of a transmission queue associated with each communication port makes it possible to avoid data collisions during transmission, for example, when the communication node receives data frames simultaneously on several communication ports, the data corresponding to these data frames are sent to the transmission queues by the processing unit 16. The data is then transmitted by the corresponding communication ports according to a FIFO (First In, First Out) principle.
Each communication node of the communication network retransmits the data frames received, by each of the communication ports of said node, on all of its other communication ports. This makes it possible to distribute, in the communication network, a data frame transmitted by a subscriber. In particular, in the case of a non-limiting exemplary communication network 20, such as the one shown in
In a particular example embodiment, subscribers of the set of subscribers are configured for communicating on the network according to a communication protocol compatible with the ARINC 664 part 7 standard. As already indicated, this standard provides virtual links for the exchanges of data frames between the subscribers of the communication network: a subscriber transmits data frames on a virtual link to one or more receiving subscribers and each virtual link is allocated with a maximum bandwidth. A virtual link uses physical links of the communication network and passes through one or more communication nodes. Several virtual links can use a same physical link as long as the total of the maximum bandwidths allocated to these virtual links does not exceed the bandwidth supported by that physical link. In a particular example embodiment, the authorized maximum bandwidth for transmission on the network associated with a subscriber of the network corresponds to the total of the maximum bandwidths allocated to the defined virtual transmission links for that subscriber. Consequently, the condition according to which the total of the authorized maximum bandwidths corresponding to each of the subscribers is less than or equal to said specified bandwidth, for example 100 Mbits/s, is equivalent to a condition according to which the total of the maximum bandwidths allocated to each of the virtual links defined in the network is less than said specified bandwidth. During the design of such a network, it is therefore appropriate to define the different virtual links in compliance with this condition and the different subscribers of the communication network must be configured consequently. In order to do this, the subscribers conventionally comprise virtual link configuration tables. Once the subscribers are thus configured, no configuration of the communication nodes is necessary. This makes it possible to simplify the design the evolution of the communication network in comparison with the networks of the prior art compatible with the ARINC 664 part 7 standard, since it is not necessary to configure paths of the virtual links in switches of the network. Unlike the networks of the prior art, when a subscriber of the network transmits a data frame on a virtual link, that data frame is distributed on all of the physical links 14 of the network. That frame is therefore received by all of the other subscribers of the network. The other subscribers use their configuration tables to determine whether to accept the received frame, for example, only the receiving subscribers of the virtual link in question accept the reception of the data frame. Given that each data frame is distributed on all of the physical links of the network, the network is robust when there is a failure of some of the physical links. In this particular example embodiment, the identifier associated with a data frame can for example correspond to the combination of a virtual link identifier and a sequence number of the frame.
In another example embodiment, the communication network is of the full-duplex Ethernet type. The identifier associated with a data frame can for example correspond to the combination of the source Ethernet address corresponding to the subscriber having transmitted that data frame with a frame number generated by that subscriber, this frame number being for example contained in an IP (Internet Protocol) header field of the frame.
In an example embodiment shown in
Advantageously, the communication node 10 is integrated in a subscriber 32 of the communication network, as shown in
The integration of the communication node 10 in the subscriber 32 makes it possible to simplify the communication network, such that the communication network does not need specific equipment for implementing the functions of a communication node. As shown in
While at least one exemplary embodiment of the present invention has been shown and described, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of the invention described herein. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. In addition, in this application, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number and the term “or” means either or both. Furthermore, characteristics or steps which have been described with reference to one of the above exemplary embodiments may also be used in combination with other characteristics or steps of other exemplary embodiments described above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 15 52568 | Mar 2015 | FR | national |
