Which three elements are field in a basic Ethernet data frame? (Choose three.)
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A. B. C. D. E. F.ABD
The correct answers are A. Preamble, B. Frame Check Sequence, and D. Length/Type.
A. Preamble: The preamble is a sequence of 7 bytes that is added to the beginning of the Ethernet data frame. It is used to synchronize the clocks of the transmitting and receiving devices. The preamble consists of a 56-bit pattern of alternating 1s and 0s, followed by a final 8-bit byte that indicates the start of the frame.
B. Frame Check Sequence: The Frame Check Sequence (FCS) is a 4-byte field that is added to the end of the Ethernet data frame. It is used to check the integrity of the frame during transmission. The FCS field contains a cyclic redundancy check (CRC) value that is computed by the transmitting device. The receiving device computes the CRC value for the received frame and compares it with the value in the FCS field. If the two values match, the frame is considered to be error-free.
D. Length/Type: The Length/Type field is a 2-byte field that immediately follows the preamble. It indicates the length of the data field in the Ethernet frame, or specifies the type of protocol that is encapsulated in the data field. If the value of the Length/Type field is less than or equal to 1500, it indicates the length of the data field. If the value of the Length/Type field is greater than 1500, it specifies the protocol that is encapsulated in the data field. For example, a value of 0800 indicates that the data field contains an IPv4 packet.
C. Header Checksum, E. Time to Live, and F. Version are not fields in a basic Ethernet data frame. Header Checksum is a field in the IP header, Time to Live is a field in the IP header, and Version is a field in the IP header as well. These fields are used in the IP layer, which is a higher layer than the Ethernet layer in the networking protocol stack.