Networking Fundamentals

A network connects devices so they can exchange data. The devices do not need matching hardware or operating systems. They need shared protocols and a path between them.

Networking turns one application message into smaller units that different devices can handle. Each unit carries control information. Switches use local addresses. Routers use network addresses. Destination hosts use port numbers to deliver data to the right application.

This course gives you the mental model behind that journey. You will learn what each layer does, how common network devices fit together, and how core services make a network usable. You will also learn where failures hide and which measurements describe user experience.

Start with the packet journey

Suppose your laptop requests a web page from a remote server.

1. The application needs the server's IP address. DNS maps the server name to an address.
2. The transport layer prepares communication for the destination application. TCP can provide a reliable, in-order byte stream. UDP sends independent datagrams with fewer transport features.
3. IP creates a packet with source and destination IP addresses.
4. Your laptop decides whether the destination is local. A remote destination goes to the default gateway.
5. The link layer places the packet inside a frame for the next hop.
6. A switch forwards that frame within the local network.
7. A router removes the incoming link header, chooses a route, and creates a new frame for the next link.
8. The destination host processes the headers in reverse order and gives the data to the destination application.

The IP packet can cross many links. Its link-layer frame changes at each routed hop. This distinction explains why a MAC address handles local delivery while an IP address handles delivery across networks.

Use layers to divide the work