Final answer:
To satisfy the minimum Ethernet frame size requirement of 64 bytes, 4 bytes of padding must be added to a 42-byte data payload received by the Ethernet MAC sublayer.
Step-by-step explanation:
The question pertains to the Ethernet frame structure in the context of data transmission. When the Ethernet MAC sublayer receives data from the LLC sublayer, there is a minimum frame size requirement. The minimum Ethernet frame size is 64 bytes, which includes the data payload, padding, and other frame encapsulation overhead like the preamble, start frame delimiter (SFD), destination MAC, source MAC, length/type field, and Frame Check Sequence (FCS). Since the data payload is mentioned to be 42 bytes and non-payload fields account for 18 bytes (6 bytes for destination MAC + 6 bytes for source MAC + 2 bytes for length/type field + 4 bytes for FCS), this totals to 60 bytes. So to reach the minimum frame size, at least 64 - 60 = 4 bytes of padding must be added to the data.
In Ethernet MAC sublayer, data is transmitted using Ethernet frames. An Ethernet frame consists of a header, data, and a trailer. The maximum payload size in an Ethernet frame is 1500 bytes. In this case, if 42 bytes of data is received from the LLC sublayer, padding is added to make the total size of the Ethernet frame equal to 1500 bytes.
Therefore, the number of bytes of padding that must be added can be calculated by subtracting the size of the received data (42 bytes) from the maximum payload size (1500 bytes). So, 1500 - 42 = 1458 bytes of padding must be added.