Relay Device Frame Recognition in Mixed Protocol Networks
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Solution Overview
Problem
In in-vehicle network systems, data frames from different communication protocols can be misrecognized due to erroneous identification of data at the tail end of Ethernet data frames, leading to potential frame recognition failures.
Innovation Solution
A relay device and communication network system that recognizes CAN frames within Ethernet frames by using a unique data storage area behind the frames, avoiding frame recognition processes in areas containing counter values and MACs, and setting a predetermined storage area longer than the unique data length to prevent misidentification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the relay device performs frame recognition process on all data in the Ethernet frame payload, then complete frame identification is achieved, but data at the tail end may be erroneously recognized as a CAN frame
Solution Approach 1:
The payload of the Ethernet frame is segmented into two distinct areas: a first area for storing CAN frames and a second area for storing unique data (such as counter values and MACs). The relay device performs frame recognition processes only on data in the first area, while excluding the second area from such processes. This segmentation prevents unique data at the tail end from being erroneously recognized as CAN frames, thereby resolving the contradiction between complete frame identification and prevention of erroneous recognition.
2Reliability
If the relay device excludes a storage area from frame recognition process, then misidentification of unique data is prevented, but the storage area must be set longer than the unique data length
Solution Approach 1:
The relay device is configured with a predetermined storage area for unique data that is set longer than the actual unique data length before data transmission occurs. This preliminary configuration ensures that even if the exact length of unique data varies, there is always sufficient space allocated to prevent misidentification. By pre-configuring the storage area with adequate length, the system maintains frame recognition reliability without requiring complex dynamic adjustments during operation.
Data Source
AI summary
A relay device includes a relay connected between a first communication network and a second communication network. The second communication network uses a communication protocol different from the first communication network. A first frame is transmitted in the first communication network, and has a first payload including control information, a first data ID for identifying the control information, and a data length code indicating a data length of the first payload. A second frame is transmitted in the second communication network, and has the first frame, a second data ID indicating that the first frame is included, and unique data stored in a predetermined storage area at a position behind the first frame. The relay recognizes the first frame without performing a frame recognition process on the data in the predetermined storage area when recognizing the first frame in the second frame on a basis of the data length code.