Abstract:
There is provided a network device for processing data packets transmitted between nodes of a network, the network device to intercept data packets of a first traffic class transmitted by a first network node and addressed to a second network node, convert the intercepted data packets into data packets of a second traffic class, and transmit the converted data packets to the second network node.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to European Patent Application No. EP 16177513, entitled “STREAM RESERVATION CLASS CONVERTER,” and filed on Jul. 1, 2016, the entire contents of which are hereby incorporated by reference for all purposes. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to a network device for processing data packets transmitted between nodes of a network, in particular in an Ethernet Audio Video Bridging (AVB) network or a Time Sensitive Network (TSN). 
       BACKGROUND 
       [0003]    Audio Video Bridging (AVB) is a networking protocol pertaining to streaming audio and/or video data via a network (e.g., an Ethernet network), described in IEEE 802.1 standards. An AVB network may include one or more talkers (e.g., transmitter nodes) and one or more listeners (e.g., receiver nodes) for transmitting and receiving audio/video data according to the Audio/video transport protocol (AVTP), described in the IEEE 1722 standard. 
         [0004]    Similarly, Time-Sensitive Networking (TSN) is a set of IEEE 802 Ethernet sub-standards. These standards enable deterministic real-time communication over Ethernet. Time-Sensitive Networking ensures a bounded maximum latency for scheduled traffic through switched networks. Possible applications include converged networks with real time Audio/Video Streaming and real-time control streams which are used in automotive or industrial control facilities. 
         [0005]    When audio/video data is transmitted from a talker to a listener, the data may pass through hops (e.g., bridges or switches) located in the network. For example, the network may comprise bridges that receive the data, determine a next location (e.g., a next bridge), and send the data to the next location toward the listener. The time the data takes to be transmitted from the talker to the listener, including the time taken for the bridge(s) to perform these actions, constitutes a latency. 
         [0006]    One of the features of AVB and TSN networks is the definition of Quality of Service (QoS) requirements and associated traffic or Stream Reservation (SR) classes. 
         [0007]    Each traffic class defines a maximum latency based on the presence of a maximum number of seven hops between the talker and the listener in the network. The latency includes the accumulated time it takes for the data to transit through the switches (accumulated transit time). The maximum latency may include the accumulated transit time plus a predetermined margin. 
         [0008]    For example, AVB traffic class A is the highest class and defines a maximum latency of 2 ms over seven hops. Traffic class A is particularly suited for the transmission of low latency audio data. Traffic class B defines a maximum latency of 50 ms over seven hops and can be used for the transmission of video data. Additional, lower traffic classes include so-called traffic class 64Sample 48 kHz (Class 64x48k) and traffic class  64 Sample 44.1 kHz (Class 64x44.lk). These classes can define even lower maximum latencies. 
         [0009]    Examples of traffic classes in the context of AVB are described in Automotive Ethernet AVB Functional and Interoperability Specification Revision 1.4. 
         [0010]    Generally, relative to the other classes, the transmission of data of a higher traffic class (e.g. AVB traffic class A) causes a relatively higher processing (e.g., interrupt) load on the listener node. However, in some networks, not all listener nodes have the performance required to process such high class traffic. 
         [0011]    The present invention aims to address this problem. 
       SUMMARY 
       [0012]    According to one aspect of the present invention, there is provided a network device for processing data packets transmitted between nodes of a network, the network device to intercept data packets of a first traffic class transmitted by a first network node and addressed to a second network node, convert the intercepted data packets into data packets of a second traffic class, and transmit the converted data packets to the second network node. 
         [0013]    The network device of the present invention enables network nodes, in particular a listener designed for a certain traffic class to receive and process data packets having a different traffic class. 
         [0014]    Thus, the present provides interoperability between two network nodes or devices implemented for different traffic classes. The interoperability may be considered achieved if the lower traffic class node satisfies criteria normally associated with the higher traffic class node only, e.g. satisfying a predetermined latency threshold. However, the interoperability may also be achieved if other criteria are satisfied, for example reduced latency so that a user does not perceive any delay in the replay of an audio and/or video signal. 
         [0015]    In one embodiment, the network is an Audio Video Bridging (AVB) network, wherein the first and second traffic classes are Stream Reservation (SR) classes, and in particular wherein the first traffic class is AVB class A and the second traffic class is a relatively lower AVB traffic class. As described above, AVB networks support different QoS requirements associated with respective SR classes. The present embodiment enables an integration of talker and listener nodes having different QoS requirements and SR classes in a single network without having to modify the talker and/or listener nodes. 
         [0016]    In another embodiment, the network is a Time Sensitive Networking (TSN) network. However, the present invention is not limited to AVB or TSN networks. Rather, the present invention can be implemented in other Ethernet or wireless networks comprising nodes of different traffic classes, in particular different latency and/or QoS requirements. The present invention provides interoperability between such nodes. 
         [0017]    In an embodiment, the second traffic class is lower than the first traffic class. In particular, the second traffic class may have a lower QoS and/or latency requirement. 
         [0018]    Thus, it is possible to add talker nodes or services to an existing network that require a high traffic class while retaining nodes that only support a relatively lower traffic class. This approach allows the use of legacy devices, for example older backward compatible listener devices. 
         [0019]    In an exemplary embodiment, the network device is a bridge device. In this embodiment, existing networks may easily be modified to include such bridge device. 
         [0020]    According to another aspect of the present invention, there is provided a network for streaming audio and/or video data, the network comprising: a first network node for generating and transmitting data packets of a first traffic class; a second network node for receiving data packets of a second traffic class; and a network device according to any one of the embodiments described above, the network device arranged between the first and second network nodes. 
         [0021]    Accordingly, there is provided a network in which a talker is enabled to communicate with a listener despite regardless of different latency requirements. In particular, a talker can transmit data packets of a higher traffic class regardless of whether the intended recipient supports that traffic class. 
         [0022]    In an embodiment the network comprises a network switch, wherein the network device is included in the network switch. Accordingly, the network device can be implemented by a software component in an existing network switch. 
         [0023]    In an embodiment, the network is an automotive network. Automotive networks are usually closed networks containing a fixed number of switches. In particular, an automotive network contains less than three switches, down to only a single switch. Accordingly, in a particular embodiment of the invention, the network is a closed network containing a single network switch. Data packets transmitted by a talker device in such network need to pass one hop only (the switch). As a consequence, the actual maximum latency is only a fraction (e.g. one seventh) of the maximum latency over seven hops generally required in AVB networks. Thus, data packets can be processed by a listener in accordance with a lower traffic class while satisfying latency requirements of a relatively higher traffic class. For example, a traffic class requiring a latency of  14 ms (or less) over seven hops can be used to achieve a maximum latency of 2 ms (or less) over one hop, thereby satisfying the general latency requirement for AVB class A traffic ( 2 ms over seven hops). As a consequence, a data packet can be transmitted by a talker in a higher traffic class and processed by a listener in accordance with a relatively lower traffic class. 
         [0024]    In an embodiment, the network comprises a head unit of an automotive system, wherein the network device is included in the head unit, in particular in a network switch of the head unit. Accordingly, the present invention may easily be implemented by adding a software component to the head unit in an automotive network. 
         [0025]    In another embodiment the network further comprises three or more network nodes, wherein the network device forms the only hop or switch or bridge between the first and second network nodes. In other words, the network device may also be employed in an open network and/or a network comprising multiple hops or switches, wherein the network device is arranged between the first and second network nodes such that there are no further hops between the network device and the first and second network nodes. 
         [0026]    According to another aspect of the present invention there is provided a method of processing data packets in a network, the method comprising: intercepting data packets of a first traffic class transmitted by a first network node and addressed to a second network node, converting the intercepted data packets into data packets of a second traffic class, and transmitting the converted data packets to the second network node. 
         [0027]    In an embodiment, the method is implemented in an Audio Video Bridging (AVB) network, wherein the first and second traffic classes are Stream Reservation (SR) classes, and the second traffic class is lower than the first traffic class, and in particular wherein the first network class is AVB class A and the second network class is a relatively lower AVB class. 
         [0028]    In another embodiment, the network is a TSN. However, the method may also be applied to other Ethernet or wireless networks comprising nodes of different traffic classes. 
         [0029]    In accordance with another aspect of the present invention, there is provided a computer-program product having a non-transitory computer readable medium storing computer executable code which, when executed by computer, causes the above method to be performed. Accordingly, the method may be software-implemented, for example in a network switch of an automotive network. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    The present invention may be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein: 
           [0031]      FIG. 1  schematically shows an example network in accordance with an embodiment of the present invention; and 
           [0032]      FIG. 2  is a flow chart for an example method in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0033]    An AVB network may include talker and listener devices constituting nodes of the network. The talker device may transmit traffic class A audio/video packets intended for the listener device. A network device intercepts the data packets, converts them into data packets of a lower traffic class, and forwards them to the listener. 
         [0034]      FIG. 1  shows an AVB network  100  in accordance with an embodiment of the invention. The network  100  includes a talker device  120  and a listener device  130 . The listener device  130  forms an end node of the network  100 . A network device  140  which may be implemented as a switch is arranged between the talker device  120  and the listener device  130 . 
         [0035]    The talker device  120  may be any suitable device for sending an audio/video stream to the listener device  130  and the listener device  130  may be any suitable device for receiving and playing back the audio/video stream. For example, talker device  120  may be implemented by an in-vehicle computing system, e.g., an infotainment system, and the listener device  130  may be linked to or implemented as part of a speaker device. 
         [0036]    The talker device  120  includes a transmission buffer  121  configured to store the data packets of an audio/video stream, a communication interface  122  to transmit the data packets in the AVB network  100 , and a controller  123  to control the transmission of data packets from the buffer  121  via the communication interface  122 . 
         [0037]    The listener device  130  includes a reception buffer  131  configured to store data packets received through a communication interface  132 , and a processor  133  to process the data packets stored in the buffer  131 . For example, the processor  133  may be configured to effect a conversion of the information contained in the data packets into an output audio signal. 
         [0038]    The network device  140  comprises first and second communication interfaces  141  and  142  to receive data packets from the talker device  120  and to transmit data packets to the listener device  130 , respectively. Also, the network device  140  comprises a buffer  143  to store data packets received from the talker device  120  and data packets awaiting transmission to the listener device  130 . In addition, the network device  140  comprises a processing device  144  configured to process data packets stored in the buffer  143 , thereby to change the traffic class of selected ones or all of the data packets in the data buffer  143 . For example, the data packets may each comprise a header including a field whose bits define a traffic class. The processing device  144  may be configured to change the bits of that field thereby to change the traffic class from a first class to a second class. The second class may be a “lower” class, i.e. a class defining a higher maximum latency. For example, the first class may be AVB class A, and the second class may be AVB class B or AVB class 64x48k or 64x44.lk. As a result, the data packets stored in the buffer  143  are converted from data packets of a first traffic class into data packets of a second traffic class. Further, the processing device  144  is configured to effect an onward transmission of the converted data packets to the listener device  130 . 
         [0039]    In operation of the AVB network  1  illustrated in  FIG. 1 , the talker device  2  schedules a data packet for transmission to the listener device  130  and transmits it via the communication interface  122 . The data packet may contain audio and/or video information, and the relevant field in data packet header may be set so as to define AVB traffic class A for that data packet. The data packet is intercepted by the network device  140  and converted into a data packet of a different, lower class. In particular, the network device  140  changes the bits in the relevant field of the intercepted data packet so as to define AVB traffic class B or 64x48k or 64x44.lk. The converted data packet is then forwarded to the listener device  130  which processes the received data packet in accordance with the traffic class defined in the packet header. 
         [0040]    The communication between the various devices of the AVB network  100  may be implemented in accordance with Ethernet AVB protocols. In particular, the communication may be implemented in accordance with IEEE 802.1Qat-2010 for the stream reservation protocol (SRP). 
         [0041]      FIG. 2  is a flowchart illustrating a method  200  in accordance with an embodiment of the present invention. The method may be performed by a network device arranged in an AVB network between a talker and a listener, such as the network device  140  described in connection with  FIG. 1 . 
         [0042]    At  210  the method includes receiving a data packet from a talker device in an AVB network. The data packet is intended for a listener device in the AVB network and has an AVB traffic class A. At  220  the method includes converting the data packet received at  210  into a data packet having an AVB class B or 64x48k or 64x44.lk. This is done by changing the control bits in the header of the data packet setting the traffic class. At  230  the method includes transmitting the converted data packet to the listener device for which the data packet was intended. The listener device can then process the received data packet as an AVB class B or 64x48k or 64x44.lk data packet. 
         [0043]    The description of embodiments has been presented for purposes of illustration and description. Suitable modifications and variations to the embodiments may be performed in light of the above without departing from the scope of protection as determined by the claims. 
         [0044]    In particular, whilst some of the above examples are described in connection with AVB networks, the present invention can also be implemented in TSN networks or other networks having pre-defined different traffic classes, in particular automotive networks. In such networks, the present invention achieves interoperability between nodes or devices requiring or implemented for different traffic classes.