Quiz Entry - updated: 2026.07.14
What are the three parts of a Data Link frame?
Header (control info and addresses), Data (the Layer 3 packet payload), and Trailer (error detection).
Data is encapsulated by the Data Link Layer with a header and a trailer to form a frame.
* A frame is a header (addresses + control), the data payload, and a trailer (error detection). *
Three parts of a frame:
| Part | Position | Purpose |
|---|---|---|
| Header | Beginning | Contains control information — typically the frame start delimiter, source and destination addresses (MAC), and a type/length field |
| Data | Middle | Contains the frame payload (Layer 3 packet) |
| Trailer | End | Contains error detection information |
Note: The fields of the header and trailer vary according to the data link layer protocol used.
Go deeper:
Ethernet frame (Wikipedia) — concrete worked example of the three-part structure: header (preamble, SFD, MAC addresses, type) / payload / FCS-trailer, with an octet table.- Frame (networking) (Wikipedia) — protocol-agnostic definition: sync bits + packet payload + frame check sequence.