46 lines
1.9 KiB
Markdown
46 lines
1.9 KiB
Markdown
# OSI Model
|
|
The OSI Model is a layered protocol model. It was proposed by the International Organization for Standardization. The model can be used as a reference to understand how networks operate.
|
|
|
|
![[OSI-model.png]]
|
|
|
|
The model was created to have a standard which hardware/software producers could use so that different products could work with each other.
|
|
|
|
For example, before this model was introduced, hardware from company A could not work together with hardware of company B because the protocols and techniques used were completely different.
|
|
|
|
As you can see the model has 7 layers. Each layer has their own responsibility.
|
|
|
|
**Note: We don't actually "use" the OSI model, we mostly use the [[TCP/IP Model]] now. The implementation is exactly the same, only some layers are different.**
|
|
|
|
## 7. Application Layer
|
|
The application Layer provides services to the end user. So this is the layer the user actually interacts with.
|
|
|
|
These services are usually protocols that interact with the data that the user uses.
|
|
|
|
**Examples of services (protocols):**
|
|
- HTTP
|
|
- FTP
|
|
- IRC
|
|
- SSH
|
|
- DNS
|
|
- SMTP
|
|
|
|
For example a web browser like Google Chrome uses the HTTP protocol to browse files on the internet. And the mail client Outlook uses the SMTP protocol to send mail via the internet.
|
|
|
|
## 6. Presentation Layer
|
|
The presentation layer is responsible for preparing the data so that it can be used by the Application Layer.
|
|
|
|
**Presentation layer is responsible for:**
|
|
- Translation of data
|
|
- Encryption of data
|
|
- Compression of data
|
|
|
|
For example, two devices can use different types of encoding on their data, the presentation layer will translate the data in a way that the Application Layer can understand.
|
|
|
|
When sending sensitive data, we would like to encrypt the data so that its secure. The Presentation layer is responsible for encrypting and decrypting ingoing or ou
|
|
|
|
|
|
## 5. Session Layer
|
|
## 4. Transport Layer
|
|
## 3. Network Layer
|
|
## 2. Data Link Layer
|
|
## 1. Physical Layer |