The Data Link Layer is often divided into two sublayers: the Logical Link Control (LLC) sublayer and the Media Access Control (MAC) sublayer. These sublayers work together to provide services and functionalities necessary for reliable communication over a physical link. Let's delve into each sublayer:

• Logical Link Control (LLC) Sublayer:
  • Provides services to the Network Layer (Layer 3) above it.
  • Offers a reliable link between two network devices.
  • Responsible for error control, flow control, and framing at the logical level.

Functions:

• Error Control: The LLC sublayer may perform error detection and correction at the logical link level, ensuring the integrity of data transferred between devices.
• Flow Control: Manages the flow of data between devices, preventing fast senders from overwhelming slower receivers.
• Framing: Encapsulates network layer packets into frames at the logical level.

Protocols: Examples of protocols operating at the LLC sublayer include:

• IEEE 802.2 (used in IEEE 802 networks like Ethernet)
• HDLC (High-Level Data Link Control)
• PPP (Point-to-Point Protocol)

• Media Access Control (MAC) Sublayer:
  • Handles access to the physical medium (e.g., cable or wireless channel).
  • Provides unique addressing (MAC addresses) for devices on the same network.
  • Controls how devices gain access to the shared communication medium.

Functions:

• Addressing: Assigns and manages MAC addresses, which are hardware addresses unique to each network interface card (NIC).
• Access Control: Manages access to the physical medium to avoid data collisions in shared network environments.
• Frame Delimiting: Defines the start and end of frames, assisting in the extraction of data from the bitstream.

Protocols: Examples of protocols operating at the MAC sublayer include:

• Ethernet (IEEE 802.3)
• Token Ring (IEEE 802.5)
• Wi-Fi (IEEE 802.11)