OSI Model

Layer 1 - Physical

The Physical Layer (Layer 1) defines the specifications needed for activating, maintaining, and deactivating the physical link between end devices

• Conveys the bit stream through the network at the electrical, mechanical, and optical level
• Often uses Copper or Fiber
• Sends binary data in a bitstream

Layer 2 - Data Link

The Data Link Layer (Layer 2) defines how data is formatted for transmission and how access to physical media is controlled

• Frames are encoded and decoded into bits at Layer 2.
• Provides error detection for Layer 1

Layer 3 - Network

The Network Layer (Layer 3) is responsible for routing packets to their destination and for QoS. It also provides connectivity and path selection between two host systems that may be located on geographically separated networks.

Layer 4 - Transport

The Transport Layer (Layer 4) provides transparent transfer (i.e. transport) of data between hosts and is responsible for end-to-end recovery and flow control. It defines services to segment, transfer, and reassemble the data for individual communications between the end devices.

Layer 5 - Session

The Session Layer (Layer 5) establishes, manages, and terminates sessions between two communicating hosts

Layer 6 - Presentation

The Presentation Layer (Layer 6) ensures that the information that is sent at the application layer of one system is readable by the application layer of another system.

Layer 7 - Application

The Application Layer (Layer 7) provides network services to the applications of the user