Lecture Notes: Understanding Common Port Numbers and Protocols

Introduction

• Importance of Port Numbers
  • Services use specific port numbers for communication.
  • Known as 'well-known port numbers' because both server and client need to know them.
  • Firewalls use port numbers to decide on allowing traffic.
  • Memorizing port numbers may initially seem difficult but becomes easier with use.

Key Protocols and Their Port Numbers

File Transfer Protocol (FTP)

• Purpose: Transfers files between devices.
• Ports:
  • TCP 20: For data transfers.
  • TCP 21: For control of data transfer.
• Authentication: Requires login, possibly anonymous.
• Functions: File management including listing, adding, deleting, and renaming.

Secure Shell (SSH)

• Purpose: Secure terminal connection to a remote device.
• Port: TCP 22.
• Security: Encrypted communication.

Telnet

• Purpose: Terminal connection to a remote console.
• Port: TCP 23.
• Security: Non-encrypted communication, not recommended for production networks.

Simple Mail Transfer Protocol (SMTP)

• Purpose: Email communication between servers and clients.
• Port: TCP 25.
• Sending vs. Receiving: Used for sending, receiving typically uses IMAP or POP3.

Domain Name System (DNS)

• Purpose: Resolves domain names to IP addresses.
• Port: UDP 53.

Dynamic Host Configuration Protocol (DHCP)

• Purpose: Automatically assigns IP addresses.
• Ports: UDP 67 and UDP 68.
• Functionality: Uses a leasing system for IP addresses with possible reservations.

Hypertext Transfer Protocol (HTTP/HTTPS)

• Purpose: Web communication.
• Ports:
  • HTTP (unencrypted): TCP 80.
  • HTTPS (encrypted): TCP 443.

Post Office Protocol Version 3 (POP3)

• Purpose: Receiving email messages.
• Port: TCP 110.

Internet Message Access Protocol Version 4 (IMAP4)

• Purpose: Synchronizing email access across multiple devices.
• Port: TCP 143.

Server Message Block (SMB)

• Purpose: File and printer sharing in Windows.
• Alternate Name: Common Internet File System (CIFS).
• Ports and Methods:
  • NetBIOS over TCP/IP: UDP 137 (name service), TCP 139.
  • Direct SMB: TCP 445.

Simple Network Management Protocol (SNMP)

• Purpose: Network management and monitoring.
• Ports:
  • Queries: UDP 161.
  • Alerts (traps): UDP 162.
• Versions:
  • SNMPv1: Non-encrypted.
  • SNMPv2: Bulk transfers, non-encrypted.
  • SNMPv3: Encrypted, secure.

Lightweight Directory Access Protocol (LDAP)

• Purpose: Directory querying.
• Port: TCP 389.
• Usage: Used in Microsoft Active Directory.

Remote Desktop Protocol (RDP)

• Purpose: Remote desktop access and management.
• Port: TCP 3389.
• Compatibility: Available on various operating systems (Windows, Linux, macOS).

Conclusion

• Understanding these port numbers and protocols is crucial for network communication and management.
• Familiarity with these concepts will aid in both practical applications and exam contexts.