Hexworth Prime
House of Forge
Network Ports & Protocols
CompTIA A+ Core 1 (220-1101) • Domain 2.0 Networking
Key Concepts:
TCP vs UDP
Well-Known Ports
Protocols
OSI Model
TCP vs UDP
TCP (Transmission Control Protocol)
- Connection-oriented
- 3-way handshake (SYN, SYN-ACK, ACK)
- Guaranteed delivery
- Error checking & retransmission
- Slower but reliable
Use cases: Web, email, file transfer
UDP (User Datagram Protocol)
- Connectionless
- No handshake
- No delivery guarantee
- No retransmission
- Faster but unreliable
Use cases: Streaming, gaming, DNS, VoIP
A+ Exam Tip: TCP = reliable (like registered mail), UDP = fast (like postcards). DNS uses UDP for queries but TCP for zone transfers.
Essential Ports (MUST KNOW!)
| Port | Protocol | Service | Description |
|---|---|---|---|
| 2021 | TCP | FTP | File Transfer (20=data, 21=control) |
| 22 | TCP | SSH/SFTP | Secure Shell, Secure FTP |
| 23 | TCP | Telnet | Remote access (INSECURE!) |
| 25 | TCP | SMTP | Send email |
| 53 | TCP/UDP | DNS | Domain Name System |
| 6768 | UDP | DHCP | Dynamic IP assignment |
| 80 | TCP | HTTP | Web traffic (unencrypted) |
| 110 | TCP | POP3 | Receive email (downloads) |
| 143 | TCP | IMAP | Receive email (syncs) |
| 443 | TCP | HTTPS | Secure web traffic (TLS/SSL) |
| 445 | TCP | SMB/CIFS | Windows file sharing |
| 3389 | TCP | RDP | Remote Desktop Protocol |
TCP Connection-oriented
UDP Connectionless
BOTH Uses both
Email Ports
| Protocol | Standard Port | Secure Port | Purpose |
|---|---|---|---|
| SMTP | 25 | 465 (SSL) / 587 (TLS) | Sending email |
| POP3 | 110 | 995 | Receiving (downloads to client) |
| IMAP | 143 | 993 | Receiving (syncs with server) |
POP3 vs IMAP: POP3 downloads and (usually) deletes from server - single device. IMAP syncs and keeps on server - multiple devices.
Secure vs Insecure
| Insecure Protocol | Port | Secure Alternative | Port |
|---|---|---|---|
| FTP | 21 | SFTP/FTPS | 22 / 990 |
| Telnet | 23 | SSH | 22 |
| HTTP | 80 | HTTPS | 443 |
| SNMP v1/v2 | 161 | SNMP v3 | 161 |
Port Ranges
| Range | Name | Description |
|---|---|---|
| 0-1023 | Well-Known Ports | Reserved for common services (HTTP, FTP, etc.) |
| 1024-49151 | Registered Ports | Assigned by IANA to applications |
| 49152-65535 | Dynamic/Private Ports | Ephemeral ports for client connections |
Additional Important Ports
Network Services
| 69 | TFTP | Trivial FTP |
| 123 | NTP | Time sync |
| 161 | SNMP | Monitoring |
| 389 | LDAP | Directory |
| 636 | LDAPS | Secure LDAP |
Remote Access
| 5900 | VNC | Remote desktop |
| 3389 | RDP | Windows remote |
| 1701 | L2TP | VPN tunneling |
| 500 | IKE | IPsec key exchange |
OSI Model Quick Reference
| Layer | Name | Protocols/Examples | Data Unit |
|---|---|---|---|
| 7 | Application | HTTP, FTP, SMTP, DNS | Data |
| 6 | Presentation | SSL/TLS, JPEG, ASCII | Data |
| 5 | Session | NetBIOS, RPC | Data |
| 4 | Transport | TCP, UDP | Segment |
| 3 | Network | IP, ICMP, Routers | Packet |
| 2 | Data Link | Ethernet, MAC, Switches | Frame |
| 1 | Physical | Cables, Hubs, NICs | Bits |
Mnemonic: "Please Do Not Throw Sausage Pizza Away" (Physical to Application)
Knowledge Check
Q1: Which port is used for HTTPS (secure web traffic)?
Q2: Which protocol uses both TCP and UDP?
Q3: What is the secure alternative to Telnet (port 23)?
Q4: Which port range are "well-known" ports?