Why is the minimum length of data field equal to 46 bytes (under the IEEE 802.3 standards?
Under both Ethernet and IEEE 802.3 standards, the minimum size frame must be 64 bytes in length from preamble through FCS fields. This minimum size frame ensures that there was sufficient transmission time to enable Ethernet NICs to detect collisions accurately based on the maximum Ethernet cable length specified for a network and the time required for a frame to propagate the length of the cable. Based on the minimum frame length of 64 bytes and the possibility of using two-byte addressing fields, this means that each data field must be a minimum of 46 bytes in length. The two-byte addressing is a historical feature of IEEE 802.3 standard, no longer much in use, but it has been in use in early IEEE 802.3 networks. Today, almost all IEEE 802.3 networks use six-byte addressing. Using the assumption that the address fields are two-byte long, the calculation of the minimum lenght of the data field is as follows: Preamble 8 bytes + Destination Addres 2 bytes + Source Address 2 bytes + Type
Under both Ethernet and IEEE 802.3 standards, the minimum size frame must be 64 bytes in length from preamble through FCS fields. This minimum size frame ensures that there was sufficient transmission time to enable Ethernet NICs to detect collisions accurately based on the maximum Ethernet cable length specified for a network and the time required for a frame to propagate the length of the cable. Based on the minimum frame length of 64 bytes and the possibility of using two-byte addressing fields, this means that each data field must be a minimum of 46 bytes in length. The two-byte addressing is a historical feature of IEEE 802.3 standard, no longer much in use, but it has been in use in early IEEE 802.3 networks. Today, almost all IEEE 802.3 networks use six-byte addressing. Using the assumption that the address fields are two-byte long, the calculation of the minimum lenght of the data field is as follows: Preamble 8 bytes + Destination Addres 2 bytes + Source Address 2 bytes + Type
