Lesson 2 - OSI Model Layers

https://www.youtube.com/watch?v=uE84knYoJSY&list=PLc6LqxQFwub-6z0ENNdyW4ZHSh9vfoWmY&index=3

Open Systems Interconnection Model

OSI - Rules devices/software must follow for network communication

OSI Layers

7 - Application

6 - Presentation

5 - Session

4 - Transport

3 - Network

2 - Data Link

1 - Physical

Please Do Not Throw Salami Pizza Away

Physical (1)

Sending/receiving bits of data between nodes aka data communication. Can take place via physical cables or wireless.

Specifies physical topology (how hardware remains connected) and interface (physical connection points aka rj45 or optical interfaces on the switch/router)

Data Link (2)

LAN 2/Switching/Data Link Control (DLC) Layer -

Nodes share data using a hardware/Layer 2/physical/MAC address on the same logical segment. Concentrates on data’s path and rules.

Layer 2 segments can include multiple physical segments (logical topology)

physical segment = devices connected via one layer 1 type such as mesh. Logical topology can include both a Star and Mesh topology)

*Switches forward data based on Layer 2 addresses.

*Some protocols run as DLC protocols such as MAC addresses

Devices operating on Layer 2

NIC, bridge, switch, wireless access points

Networking (3)

Associated with and makes forwarding decisions based on IP addresses

Moves data around a network of networks (inter network/Internet) and forwards data based on destination network layer address

Packets forwarded router by router (hop by hop)

*Router is a layer 3 device

First three layers are concerned with moving frames/datagrams between nodes and networks