Ports/Purpose

FTP

Used for transferring files. Port 21 is for control/commands, and port 20 is for transferring data between client and server.

SSH

Allows secure remote management of systems and is also used for SFTP and SCP file transfers.

DNS

Translates domain names to IP addresses for web browsers and other network services.

HTTP

The language web browsers use to ask for websites. It sends information in plain text, meaning anyone watching the network can read what you are looking at.

HTTPS

It scrambles the language into a secret code. It ensures that only you and the website know what is being discussed (like passwords or credit cards).

POP3

An old way to check email that downloads the message to your device and usually deletes it from the server. If you lose your phone, you lose the emails forever.

IMAP

A way to check email that keeps the original message on the server. If you read it on your phone, it is still there for your laptop to see later. It syncs everywhere.

RDP

A "remote control" for a computer. It puts a picture of another computer's screen on your monitor and lets you control the mouse and keyboard from miles away.

SMB

The feature that lets you see folders and printers on other computers in your house or office and use them as if they were plugged into your own machine.

LDAP

A digital phonebook for a company. Computers use it to look up usernames, passwords, and email addresses to verify that a user actually exists.

SNMP

A tool that checks on network equipment to see if it is working correctly. It reports back if a device is overheating, full of data, or broken.

DHCP

The system that automatically assigns a unique address to every device that joins a network so they don't clash. Without it, you'd have to manually set up every phone and laptop.

Kerberos

A security system that gives you a digital "ticket" after you log in once. You show this ticket to different servers to prove who you are, so you don't have to type your password constantly.

SFTP/SCP

Two ways to copy files securely over a text-based connection. One is for simple "copy and paste", and the other lets you actually manage the files, like deleting or renaming them.

FTPS

A standard way to move files from one computer to another, but wrapped in a layer of security so nobody can steal the data while it is moving.

PPTP

An ancient, outdated way to connect to a work network from home. It is considered very unsafe now because hackers can easily break into it.

L2TP

A way to create a direct link between two distant computers (a VPN). It builds the "pipe" but doesn't scramble the data inside to keep it safe, so it usually brings a friend along to handle the security.

IPSec

Provides secure IP communications via encryption.

TACACS+

A network security protocol that centrally handles authentication, authorization, and accounting (AAA) for administrators who log in to manage network devices like routers and switches.

RADIUS

A network security protocol that centrally handles AAA for users who are connecting to network services, such as VPNs or Wi‑Fi, to control whether and how they can access the network.