What are the two sizes (minimum and expected maximum) of an Ethernet frame

"We also know that the minimum MTU is 576 Bytes."

No, we do not know that because it is not true. I am not sure where you got such an idea.

The MTU is the maximum payload of the data-link protocol. In the case of ethernet, the IEEE standard says that is 1500 bytes. The minimum payload size is 46 bytes (42 bytes for tagged frames), but that is not a minimum MTU because the MTU is the maximum payload size, not the minimum. Remember that IP (whether IPv4 or IPv6) is not the only network-layer protocol, and ethernet is not the only data-link protocol in use for IP. Ethernet and IP were developed by different people for different reasons, and the standards are maintained by different groups, even today.

576 bytes is the minimum datagram size that hosts must be able to process for IPv4, and 1280 bytes for IPv6, but that is not the smallest MTU for ethernet. Most hosts can process IP datagrams as small as 28 bytes for IPv4 and UDP (IPv4 header of 20 bytes, UDP header of 8 bytes, and 0 data bytes) and 48 bytes for IPv6 (IPv6 header of 40 bytes, UDP header of 8 bytes and, 0 data bytes).

Both the Ethernet II and IEEE 802.3 standards define the minimum frame size as 64 bytes and the maximum as 1518 bytes. This includes all bytes from the Destination MAC Address field through the Frame Check Sequence (FCS) field. The Preamble and Start Frame Delimiter fields are not included when describing the size of a frame.

Any frame less than 64 bytes in length is considered a "collision fragment" or "runt frame" and is automatically discarded by receiving stations.

The IEEE 802.3ac standard, released in 1998, extended the maximum allowable frame size to 1522 bytes. The frame size was increased to accommodate a technology called Virtual Local Area Network (VLAN). VLANs are created within a switched network and will be presented in a later course. Also, many quality of service (QoS) technologies leverage the User Priority field to implement various levels of service, such as priority service for voice traffic. The figure displays the fields contained in the 802.1Q VLAN tag.

If the size of a transmitted frame is less than the minimum or greater than the maximum, the receiving device drops the frame. Dropped frames are likely to be the result of collisions or other unwanted signals and are therefore considered invalid.

At the data link layer the frame structure is nearly identical. At the physical layer different versions of Ethernet vary in their method for detecting and placing data on the media.

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