A student is labeling a capture taken on an access port. The unit that includes the source and destination MAC addresses needs a name. Which name is correct for that unit?
Select an answer to reveal the explanation.
Short Explanation
You name the box by the label on it, and MAC addresses live on a frame, the data-link unit. A packet is the IP envelope inside, and a segment is the TCP or UDP unit inside that. The frame check sequence is the trailer that proves the frame survived the trip, and it does not hold the MAC addresses.
Full Explanation
Each OSI layer has a name for the unit it handles. At the data-link layer the unit is a frame, and an Ethernet frame's header carries the source and destination MAC addresses plus a type or length field. The student who is labeling the unit that holds those MAC addresses should call it a frame. A packet, or IP datagram, is the network-layer unit. Its header carries IP addresses, and it sits inside the frame while the frame is on the wire. A segment is the usual name for a TCP unit at the transport layer, where sequence numbers and ports live. Neither is the unit that owns the MAC header. The frame check sequence is the tempting field-level miss. It is part of the Ethernet frame, and it is the trailer checksum, not the header field that stores the two MAC addresses. Exam caveat: people say packet for anything in a capture. On this exam the names stay with their layers, so a question that points at MAC addresses is asking for the frame. Operational check: in the analyzer, expand the Ethernet header and confirm the MAC addresses are in that header, then confirm the frame check sequence is a separate trailer field.