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Network Ports and Protocols Overview

Jun 8, 2025

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Overview

This lecture covers essential TCP and UDP port numbers, their associated protocols, and their importance in troubleshooting, firewall configuration, and network communication for A+ certification.

FTP, SSH, and Telnet

  • FTP (File Transfer Protocol) uses TCP Port 20 (data) and TCP Port 21 (control) for file transfers and administration.
  • FTP requires authentication but can allow anonymous logins for public access.
  • SSH (Secure Shell) uses TCP Port 22 to provide encrypted command-line access to remote devices.
  • Telnet uses TCP Port 23 for remote command-line access but sends data unencrypted, so it's rarely used today.

Email Protocols

  • SMTP (Simple Mail Transfer Protocol) uses TCP Port 25 for sending emails between servers.
  • POP3 (Post Office Protocol version 3) uses TCP Port 110 to download emails to clients.
  • IMAP4 (Internet Message Access Protocol version 4) uses TCP Port 143 for advanced email management and folder synchronization.

Web Protocols

  • HTTP (Hypertext Transfer Protocol) uses TCP Port 80 to send unencrypted web traffic.
  • HTTPS (Hypertext Transfer Protocol Secure) uses TCP Port 443 for encrypted web communication.

Name Resolution and Address Management

  • DNS (Domain Name System) uses UDP Port 53 to translate domain names into IP addresses.
  • DHCP (Dynamic Host Configuration Protocol) uses UDP Ports 67 (server) and 68 (client) to assign IP addresses and network settings automatically.

File and Printer Sharing (Windows)

  • SMB (Server Message Block) is used in Windows for file/printer sharing and uses TCP Port 445.
  • NetBIOS needs UDP Port 137 (name service) and TCP Port 139 (session) for older Windows communication.

Directory Services

  • LDAP (Lightweight Directory Access Protocol) uses TCP Port 389 for accessing and managing directory databases.
  • LDAPS (LDAP Secure) encrypts LDAP traffic (port not explicitly mentioned in transcript).

Remote Access

  • RDP (Remote Desktop Protocol) uses TCP Port 3389 to remotely control Windows desktops and run applications from various operating systems.

Key Terms & Definitions

  • FTP — Protocol for transferring files between devices (Ports 20, 21).
  • SSH — Secure encrypted remote command-line access (Port 22).
  • Telnet — Unencrypted remote command-line access (Port 23).
  • SMTP — Sends emails between servers (Port 25).
  • POP3 — Downloads email to clients (Port 110).
  • IMAP4 — Manages email and folders across devices (Port 143).
  • HTTP/HTTPS — Web protocols for unencrypted/encrypted data (Ports 80/443).
  • DNS — Resolves domain names to IP addresses (Port 53).
  • DHCP — Assigns IP addresses to devices (Ports 67, 68).
  • SMB — Shares files/printers in Windows (Port 445).
  • NetBIOS — Older name/session service for Windows (Ports 137, 139).
  • LDAP — Directory database protocol (Port 389).
  • RDP — Remote desktop access protocol (Port 3389).

Action Items / Next Steps

  • Memorize key port numbers and associated protocols.
  • Understand the function and security implications of each protocol.
  • Practice configuring firewalls and troubleshooting network issues using port numbers.

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