Hello Open System Interconnection (OSI) Layers

A quick and dirty on the seven layers of the OSI Model.

OSI Layers in Network Traffic

Layer 1: Physical

Represents the bit-level transmission between network nodes over the connection medium.

Data: Bits across the wire (1s and 0s) as pulse of electricity or light.

Layer 2: Data Link

Data Link Layer handles communications between adjacents network nodes via physical addressing (MAC).

Data: Frames.

Layer 3: Network

Handles routing messages (packets) via the best route to reach its destination based on IP address.

Data: Packets.

Layer 4: Transport

Defines how data will be sent providing validation and security.

Data: Segments.

Layer 5–7: Application, Presentation, Session

Layers 5–7 are typically managed by the application itself, providing the interface for the user to communicate.

Data: Data.

Data in a TCP/IP Example

  • Data Link Layer (2): Frame = Frame Header + Frame Data

When dealing with subnetting, network masks etc, note that you are working in the Network Layer (layer 3).

Get in touch with me on Twitter @dendribbles

Senior Engineer @ Culture Amp. Tinkerer and professional self-isolator in 2020.

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