Quiz Entry - updated: 2026.07.14
What are the two sublayers of the Data Link Layer in Ethernet, and what does each do?
The LLC (IEEE 802.2) identifies which network-layer protocol the frame carries and talks to the upper layers; the MAC (IEEE 802.3) handles encapsulation, addressing and media access, talking to the physical layer.
| Sublayer | Standard | Function |
|---|---|---|
| LLC (Logical Link Control) | IEEE 802.2 | Places information in the frame to identify which Network Layer protocol is being used (e.g., IPv4, IPv6) |
| MAC (Media Access Control) | IEEE 802.3, 802.11, 802.15 | Responsible for data encapsulation and media access control; provides Data Link layer addressing |
Key insight: The LLC sublayer communicates with the upper layers (Network), while the MAC sublayer communicates with the lower layer (Physical).
Go deeper:
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IEEE 802.2 / LLC (Wikipedia) — the upper data-link sublayer, including the DSAP/SSAP fields it uses to identify the carried protocol. -
Medium access control (Wikipedia) — the lower data-link sublayer: framing, addressing, and arbitrating access to the medium.