Basics of Port Addressing

Basics of Port Addressing

Port numbers help network data reach the correct process on a device. They build on IP and MAC addressing.

How addressing works

An analogy compares network delivery to sending a parcel to Mumbai, then to an apartment, and finally to a person:

• IP addresses direct data to the correct network.
• MAC addresses direct data to the correct host on the local network.
• Port numbers help the host’s operating system deliver data to the correct process or application.

Port numbers are also called port addresses or simply ports. They act as communication endpoints and range from 0 to 65,535.

Ports can be fixed (predefined) or dynamic, with dynamic ports assigned by the operating system. The specific handling of these categories is covered in later transport-layer lessons.

Example: A browser request

When a browser requests YouTube data, the request includes source and destination port numbers. The source port helps ensure that the returning data reaches the requesting browser process.

Three key points

Before sending data, a node uses:

1. Source and destination IP addresses to identify network-level endpoints.
2. Source and destination MAC addresses to identify hosts on the local network.
3. Source and destination port numbers to identify the relevant processes on those hosts.

Viewing ports in Windows

Open the Start menu, search for resmon, and launch Resource Monitor to view processes and their ports. Multiple Chrome instances may use different port numbers.

Main speaker/source: A single instructor from Neso Academy.