NIC-to-NIC communication, encapsulating Layer 3 packets into frames, and error detection that rejects corrupted frames.

The Data Link Layer (Layer 2) is responsible for:

* The Data Link Layer's three jobs: NIC-to-NIC delivery, encapsulating packets into frames, and error detection. *

1. NIC-to-NIC communications - Responsible for communications between end-device network interface cards

2. Encapsulation - Allows upper layer protocols to access the physical layer media; encapsulates Layer 3 packets (IPv4/IPv6) into Layer 2 Frames

3. Error detection - Performs error detection and rejects corrupted frames

Key insight: The Data Link Layer prepares network data for the physical network.

Go deeper:

• The OSI Model — Layer 2 (Practical Networking) — animated walk-through of how L2 groups bits into frames, adds the MAC header, and delivers hop-to-hop.
• Data link layer (Wikipedia) — covers all three duties directly: node-to-node delivery, framing/encapsulation, and error detection.
• Frame (networking) (Wikipedia) — zooms in on encapsulation: how an L3 packet becomes a frame with sync bits, payload, and frame check sequence.

LLC talks to the networking software above; MAC handles data encapsulation and access to the physical medium below.

The Data Link Layer consists of two sublayers:

* LLC faces the software above; MAC faces the medium below — both inside Layer 2. *

Visual position in OSI model:

• LLC sublayer is above MAC sublayer
• Both sit between Network Layer (above) and Physical Layer (below)

Go deeper:

• IEEE 802.2 — LLC (Wikipedia) — the primary-standard view: LLC header (DSAP/SSAP), service types, and how LLC rides above MAC.
• Logical link control (Wikipedia) — the upper sublayer in depth: it interfaces to the network-layer software above and multiplexes protocols.
• IEEE 802 (Wikipedia) — shows the canonical split of the data link layer into LLC and MAC, aligned to the OSI model.