1. Physical Layer
This is the hardware level. The Physical Layer deals with the actual transmission of bits across a network. Those bits travel through something physical or wireless, depending on the connection.
A network cable fits here. So does the electrical signal moving through it. Wi-Fi uses radio signals instead. Basically, this layer is concerned with getting raw bits from one point to another.
2. Data Link Layer
Once those bits are moving, the Data Link Layer helps devices communicate over the same local network. It works with frames and uses MAC addresses to identify devices on that network.
Ethernet and switches operate closely with this layer. If your computer needs to send data to another device sitting on the same local network, this layer matters a lot.
3. Network Layer
Here’s where things get more interesting. The Network Layer handles logical addressing and routing, which means it helps determine where data needs to go when the destination isn’t sitting right beside your computer.
IP addresses belong here. Routers also work at this layer because they make decisions about where packets should travel next.
4. Transport Layer
The Transport Layer is focused on getting data between devices reliably or quickly, depending on the protocol being used. TCP and UDP are the big names here.
TCP and UDP
• TCP is the careful one. It checks delivery because missing data can cause problems.
• UDP moves faster with less overhead, which is why it’s common in real-time traffic where waiting feels worse than losing a packet.
5. Session Layer
The Session Layer manages communication sessions between devices. It helps establish, maintain, and end those sessions when applications communicate.
6. Presentation Layer
Data sometimes needs to be translated or formatted before an application can use it. That’s where the Presentation Layer comes in.
Making Data Understandable
This layer deals with things such as data formatting and encryption. It can also handle compression. The basic idea is simple: make sure the data being exchanged is represented in a form the receiving application understands.
7. Application Layer
The Application Layer sits at the top. It interacts most closely with the software and network services you use, although it isn’t simply “the app itself.”
Protocols such as HTTP and DNS are commonly associated with this layer. So when you load a website or look up a domain name, you’re dealing with protocols that operate at the application level.