1.1 Understanding the OSI Model

Identify the 7 Layers of the OSI model and what they do

Layer 1: Physical

The physics of the network. It includes hardware components like cables, switches, and network interface cards. Fixing cables, doing loopback tests, testing/replacing cables, swap adapter cards are common solutions.

Layer 2: Data Link

The fundamental layer that’s used to communicate between two devices on the network (MAC addressing). It is the “switching” layer.

Layer 3: Network

The layer that routers use to determine how to forward traffic (“routing” layer). Includes IP addressing, subnet masks or routing problems.

Layer 4: Transport

The “post office” layer. The ability to transport information from one device to another. Includes TCP and UDP.

Layer 5: Session

Communication management between devices (start, stop, restart). Provides a session prior to sending the data across networks and devices.

Layer 6: Presentation

Responsible for putting all the data into a format that we will eventually see with our human eyes. Includes character encoding and application encryption.

Layer 7: Application

The layer we see on our screen. Uses common applications like HTTP, FTP, DNS, POP3.