This chapter tends to appear deceptively easy as we figure we just memorize each layer with some sentence phrase and bam all set.

The reality is that OSI is just an outline of a theoretical model used to place protocols and data processing at certain layers.

This can generate more complicated answers as some protocols may be primarily at a certain layer but may interact at other layers. So it is important to try to keep this at a theoretical level as nothing is black and white.

When looking at the OSI Model in reference to Protocols is to think about what occurs at that layer. Once that is understood, it is easier to figure out what Protocols may be at that layer

OSI Layer

One: Physical

Function: Binary Signal transmission over physical media

Data Unit: Bit

There is no header or tail and it is passed up to Layer 2 to become a frame

Hardware: Cables, Modems, Hub, repeater, NIC

Protocols: Ethernet, 802.11, USB, Bluetooth

Two: Data Link Layer

Function: Physical Addressing think MAC addresses

Data Unit: Frame