The Open Systems Interconnection (OSI) model divides network functions into seven layers. The Data Link Layer (Layer 2) is responsible for node-to-node data transfer and is subdivided into two sublayers: the Logical Link Control (LLC) sublayer and the Media Access Control (MAC) sublayer. The MAC sublayer interfaces directly with the Physical Layer (Layer 1) and is responsible for controlling how devices in a network gain access to the medium and for the physical addressing (MAC addresses) of network interface cards.

A. The Transport layer (Layer 4) provides end-to-end communication services for applications and is not involved with physical addressing or media access.
B. The Network layer (Layer 3) is responsible for logical addressing (e.g., IP addresses) and routing data packets between different networks.
D. The Physical layer (Layer 1) defines the physical and electrical specifications for transmitting raw bits over a medium but does not manage access or addressing.

1. IEEE Std 802-2014, IEEE Standard for Local and Metropolitan Area Networks: Overview and Architecture. Section 5.2.2, "Data Link Layer," states: "The Data Link Layer is divided into two sublayers: Medium Access Control (MAC) and Logical Link Control (LLC)." Figure 2—"Relationship of IEEE 802 standards to the OSI reference model"—visually confirms this structure.

2. Kurose, J. F., & Ross, K. W. (2021). Computer Networking: A Top-Down Approach (8th ed.). Pearson. Chapter 6, "The Link Layer: Links, Access Networks, and LANs," Section 6.1, "Introduction to the Link Layer," describes the Data Link Layer's services, including media access control.

3. Stallings, W. (2014). Data and Computer Communications (10th ed.). Pearson. Chapter 15, "Local Area Network Overview," Section 15.2, "LAN Protocol Architecture," details the IEEE 802 reference model, explicitly placing the MAC sublayer within the Data Link Layer, just above the Physical Layer.