> For the complete documentation index, see [llms.txt](https://mamawhocode.gitbook.io/aws/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mamawhocode.gitbook.io/aws/knowledge/network-knowledge/osi.md).

# OSI

Open Systems Interconnection model

## What is OSI?

OSI model is a suite of protocols, or rules, to govern how computers communicate with one another.

## Layers

<figure><img src="https://2259236002-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fuh9xZDZ53qGqmMCM44PU%2Fuploads%2FXFBgS9ggary0QyoIpURE%2Fimage.png?alt=media&amp;token=12bf54e3-3d50-4415-81ae-1fe0616b2ca5" alt="" width="375"><figcaption><p>OSI model</p></figcaption></figure>

* **Physical layer**: standards for transimitting raw data (bits)
* **Data link layer**: standards for transferring data between network nodes in WAN or LAN segment
* **Network layer** (L3): communication across different networks.
* **Transport layer**: transfer of data between users. This layer provides the ack of the successful data transmission and sends the next data if no errors occurred.
* **Session layer**: mechanism for opening, closing, and managing a session between application processes.
* **Presentation layer**: is responsible for formatting and delivering information to the application layer. It translates data based on syntax.
* **Application layer** (L7): user interacts directly with this layer.