The CAR of a switch covers the inter-frame gap and the length of VLAN tags. As the frame gap and VLAN tag length may vary, the CAR cannot be 100% accurate.
        The calculation of CAR covers the inter-frame gap and the length of VLAN tags. For example, if a tagged packet is 64 bytes, the VLAN tag is 4 bytes, and the inter-frame gap is 20 bytes, then the actual packet length is 88 bytes. The CAR error caused by the extra 24 bytes is greater.If the packet is 1000 bytes, VLAN tag is 4 bytes, and the inter-frame gap is 20 bytes, then the actual packet length is 1024 bytes. The CAR error caused by the extra 24 byte is smaller. Therefore, you are advised to use packets containing more than 1000 bytes for the test to minimize the impact of the inter-frame gap or VLAN tag length on the CAR.

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Thank you!