1.4 Explain common networking ports, protocols, services, and traffic types
Common Protocols and Ports
📘CompTIA Network+ (N10-009)
🌐 What Are Protocols and Ports?
In computer networking, protocols are standardized rules that define how data is communicated between devices over a network.
Each protocol is responsible for specific tasks, like transferring files, sending emails, or loading websites.
To identify what kind of communication is happening, each protocol uses a port number — like a “doorway” on a computer or network device that allows specific types of data traffic.
- Protocol: The communication method (like a language).
- Port Number: The specific entry or exit point for that communication.
👉 For the CompTIA Network+ exam, you must memorize the common protocols and their default port numbers, as they are frequently tested.
📘 Common Networking Protocols and Ports
Below is a detailed explanation of each key protocol, including what it does, which port it uses, and how it’s used in IT environments.
1. FTP (File Transfer Protocol) – Ports 20 and 21
- Purpose: Used to transfer files between computers over a network.
- Port 21: Control commands (authentication, directory navigation).
- Port 20: Actual data transfer.
- Type: Unencrypted (data can be intercepted).
- Use Case: Uploading or downloading files from a network file server or website hosting service.
- Exam Tip: FTP is insecure — use SFTP for secure file transfers.
2. SFTP (Secure File Transfer Protocol) – Port 22
- Purpose: Securely transfers files over an encrypted connection.
- Based On: SSH (Secure Shell).
- Use Case: Used by administrators to securely upload system backups or configuration files to remote servers.
- Exam Tip: SFTP uses the same port as SSH (22) because it operates over SSH.
3. SSH (Secure Shell) – Port 22
- Purpose: Provides secure, encrypted remote access to network devices and servers.
- Use Case: Network engineers use SSH to configure routers, switches, or servers remotely.
- Exam Tip: Replaces insecure remote access tools like Telnet.
4. Telnet – Port 23
- Purpose: Provides command-line access to remote devices (unencrypted).
- Use Case: Used historically to manage network devices before SSH became the standard.
- Exam Tip: Not secure. Never use Telnet for sensitive systems; use SSH instead.
5. SMTP (Simple Mail Transfer Protocol) – Port 25
- Purpose: Sends email messages from a client to a mail server or between mail servers.
- Use Case: Email servers use SMTP to deliver outgoing mail.
- Exam Tip: Port 25 is often blocked on public networks to prevent spam. Use Port 587 (SMTPS) for secure email submission.
6. DNS (Domain Name System) – Port 53
- Purpose: Translates domain names (like
example.com) into IP addresses. - Type: UDP for queries, TCP for larger zone transfers.
- Use Case: Every time you access a website, DNS resolves the domain name to its corresponding IP address.
- Exam Tip: DNS is critical for Internet functionality; without it, you must use IP addresses directly.
7. DHCP (Dynamic Host Configuration Protocol) – Ports 67 and 68
- Purpose: Automatically assigns IP addresses and other network settings to devices.
- Port 67: Used by the server.
- Port 68: Used by the client.
- Use Case: When a device joins a network, DHCP assigns it an IP address automatically.
- Exam Tip: Reduces manual configuration; key for managing large networks.
8. TFTP (Trivial File Transfer Protocol) – Port 69
- Purpose: A simple, lightweight file transfer protocol (no authentication).
- Use Case: Commonly used for network booting or transferring configuration files to devices like routers.
- Exam Tip: Not secure and offers no encryption or login mechanism.
9. HTTP (Hypertext Transfer Protocol) – Port 80
- Purpose: Transfers unencrypted web data between browsers and web servers.
- Use Case: Used for regular, non-secure web browsing.
- Exam Tip: Replaced by HTTPS for security reasons.
10. NTP (Network Time Protocol) – Port 123
- Purpose: Synchronizes the clocks of network devices.
- Use Case: Ensures all devices have the same accurate time for logging and authentication.
- Exam Tip: Incorrect time synchronization can cause login or certificate issues.
11. SNMP (Simple Network Management Protocol) – Ports 161 and 162
- Purpose: Used to monitor and manage network devices.
- Port 161: For SNMP agent communication (device status info).
- Port 162: For SNMP traps (alerts from devices).
- Use Case: Network monitoring tools use SNMP to collect data like CPU usage or interface status.
- Exam Tip: SNMPv3 adds encryption and authentication; older versions are insecure.
12. LDAP (Lightweight Directory Access Protocol) – Port 389
- Purpose: Used to access and manage directory information like users, groups, and permissions.
- Use Case: Active Directory (AD) uses LDAP for centralized user authentication and management.
- Exam Tip: LDAP is plaintext; LDAPS (Port 636) is secure.
13. HTTPS (Hypertext Transfer Protocol Secure) – Port 443
- Purpose: Encrypted version of HTTP using SSL/TLS.
- Use Case: Used for secure web browsing, online banking, and logins.
- Exam Tip: Always choose HTTPS over HTTP for data security.
14. SMB (Server Message Block) – Port 445
- Purpose: Enables file and printer sharing between Windows systems.
- Use Case: Used in Windows networks for accessing shared folders or printers.
- Exam Tip: SMB operates directly over TCP port 445 without using NetBIOS.
15. Syslog – Port 514
- Purpose: Used for sending system logs to a centralized log server.
- Use Case: Network devices and servers send event logs to a syslog collector for monitoring.
- Exam Tip: Syslog uses UDP and is essential for centralized log management.
16. SMTPS (Secure SMTP) – Port 587
- Purpose: Sends email securely using encryption (TLS).
- Use Case: Email clients use SMTPS to send outgoing emails safely.
- Exam Tip: Port 587 replaces the older secure mail port 465.
17. LDAPS (Lightweight Directory Access Protocol Secure) – Port 636
- Purpose: Secure version of LDAP using SSL/TLS.
- Use Case: Used by organizations that need encrypted directory authentication.
- Exam Tip: Protects user credentials and directory data during transmission.
18. SQL Server (Microsoft SQL Database) – Port 1433
- Purpose: Used by Microsoft SQL Server for database communication.
- Use Case: Applications connect to SQL databases using this port to store or retrieve data.
- Exam Tip: Firewalls often restrict access to Port 1433 for database security.
19. RDP (Remote Desktop Protocol) – Port 3389
- Purpose: Allows remote graphical access to Windows systems.
- Use Case: IT support teams use RDP to manage user desktops or servers remotely.
- Exam Tip: Always secure RDP with strong credentials or VPN access.
20. SIP (Session Initiation Protocol) – Ports 5060 and 5061
- Purpose: Sets up, manages, and ends Voice over IP (VoIP) calls.
- Port 5060: Unencrypted communication.
- Port 5061: Encrypted communication using TLS.
- Use Case: Used by VoIP phones and PBX systems for call signaling.
- Exam Tip: SIP handles call setup; actual audio uses RTP (Real-time Transport Protocol).
🧠 Exam Study Tips
- Memorize all port numbers – These are highly testable facts on the Network+ exam.
Example: SSH → 22, HTTPS → 443, DNS → 53. - Understand function and security – Know which protocols are secure (SFTP, SSH, HTTPS, LDAPS).
- Know direction – Client-to-server communications (like DHCP uses 67 for server, 68 for client).
- Relate to layers – Most of these operate at the Application Layer (Layer 7) of the OSI model.
- Compare secure vs insecure versions – e.g., HTTP vs HTTPS, LDAP vs LDAPS, FTP vs SFTP.
🏁 Summary Table
| Protocol | Port(s) | Description | Secure? |
|---|---|---|---|
| FTP | 20/21 | File transfers | ❌ No |
| SFTP | 22 | Secure file transfers | ✅ Yes |
| SSH | 22 | Secure remote access | ✅ Yes |
| Telnet | 23 | Remote access (insecure) | ❌ No |
| SMTP | 25 | Send email | ❌ No |
| DNS | 53 | Domain name resolution | ❌ No |
| DHCP | 67/68 | IP address assignment | ❌ No |
| TFTP | 69 | Simple file transfer | ❌ No |
| HTTP | 80 | Web browsing | ❌ No |
| NTP | 123 | Time synchronization | ❌ No |
| SNMP | 161/162 | Network monitoring | ❌ No (v3 is secure) |
| LDAP | 389 | Directory services | ❌ No |
| HTTPS | 443 | Secure web browsing | ✅ Yes |
| SMB | 445 | File sharing | ❌ No |
| Syslog | 514 | System logging | ❌ No |
| SMTPS | 587 | Secure email sending | ✅ Yes |
| LDAPS | 636 | Secure directory access | ✅ Yes |
| SQL Server | 1433 | Database communication | ❌ No |
| RDP | 3389 | Remote desktop | ✅ (with encryption) |
| SIP | 5060/5061 | VoIP signaling | ✅ (5061) |
