To make sense of what and where network monitoring is necessary, it helps to break it down by the OSI model — particularly focusing on Layer 2 (Data Link), Layer 4 (Transport), and Layer 7 (Application). This is the layer responsible for MAC addresses, Ethernet frames, and. In computer networks, switches are critical devices that manage the flow of data between devices in a local area network (LAN). The access layer provides initial connections to end users. When designing a campus LAN, you may choose to implement all, some, or none of the Cisco three-layer model's recommendations.