> For the complete documentation index, see [llms.txt](https://mudassirs46.gitbook.io/network-fundamentals/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mudassirs46.gitbook.io/network-fundamentals/physical-layer.md).

# Physical Layer

From amongst the [TCP-IP Layers, ](https://app.gitbook.com/@mudassirs46/s/network-fundamentals/~/drafts/-MRZ8l67L5MHnaQIEh9W/tcp-ip-layers)the First Layer is the Physical Layer.

* HTTP asks for the Web pages from a Web Server, TCP provides guaranteed delivery through Error recovery feature, Network Layer's IP provides Addressing & Routing feature for Intra-Network connectivity,  Data Link-Layer's [Ethernet ](https://app.gitbook.com/@mudassirs46/s/network-fundamentals/~/drafts/-MRZ8l67L5MHnaQIEh9W/an-ethernet)provides Inter-Network Connectivity & Physical Layer's Layer specifies the cabling and energy (for example, electrical signals) that flow over the cables for the Data-Link Layer Protocols.
* Physical Layer converts this whole Frame into binary bits Transmit them over a Physical Medium.

## Reference:

CCNA 200-301 OCG, Volume 1, Pg. 25 - Wendell Odom .