---
title: Link_Layer_of_the_Internet_Protocol
tags: [networks, internet]
created: Tuesday, August 06, 2024
---

# Link Layer of the Internet Protocol Suite

> The Link Layer is the lowest level of the network stack that makes up the
> Internet Protocol Suite. It is concerned with the physical and logical
> connections between [hosts](./Network_hosts.md) on the same local network.

The physical and logical connections are known as **Links**.

Link Layer protocols goven communication between devices. Examples include:

- **WiFi**
  - For wireless communication between devices using radio waves
- **Ethernet**
  - Wired communication

## MAC addresses

Each device on a link has a network address that uniquely identifies it. For
most Link Layer Protocols this is a Media Access Control (MAC) address.

A device receives data addressed to its MAC address.

MAC addresses are limited to local networks. Remote networks cannot send data to
a specific MAC address. This is off-limits from the outside.

## Frames

Link Layer data is divided into small units called "frames". The anatomy of a
frame is as follows:

```
--------------------------
| header | data | footer |
--------------------------
```

The header contains the source and destination MAC address plus a descriptor of
the type of data it contains. The data is the payload. The footer is used to
detect errors.