Ctrl+Alt+Route

In networking, communication between devices relies on a variety of different protocols, each serving a specific purpose. Understanding these protocols and their associated ports is essential for IT professionals, network administrators, and system administrators. In this article, we’ll break down some of the most commonly used network protocols, their functions, and the ports they use.

FTP – File Transfer Protocol

Ports: TCP/20 (Active mode data), TCP/21 (Control)
Function: FTP is a protocol used for transferring files between computers. It authenticates users with a username and password and allows operations like listing, adding, and deleting files.

SSH – Secure Shell

Port: TCP/22
Function: SSH provides an encrypted communication link, ensuring secure remote access to devices. It is widely used for remote administration and secure file transfers (via SCP and SFTP).

Telnet – Telecommunication Network

Port: TCP/23
Function: Telnet allows users to log into remote devices, but it is not secure as it transmits data in plain text. It is advisable to use SSH in most situations due to security concerns.

SMTP – Simple Mail Transfer Protocol

Port: TCP/25
Function: SMTP is used for server-to-server email transfer and is also utilized by devices to send mail to a mail server. SMTP is primarily used for sending mail, whereas POP3 and IMAP are primarily used for receiving mail.

DNS – Domain Name System

Port: UDP/53
Function: DNS converts domain names into IP addresses, allowing users to access websites using human-readable names (e.g., google.com to 8.8.8.8).

DHCP – Dynamic Host Configuration Protocol

Ports: UDP/67 & UDP/68
Function: DHCP dynamically assigns IP addresses to devices on a network, ensuring efficient and automated IP address management.

POP3 – Post Office Protocol Version 3

Port: TCP/110
Function: POP3 is used for retrieving emails from a mail server. It provides basic mail transfer functionality but does not allow multi-device inbox management.

IMAP4 – Internet Message Access Protocol v4

Port: TCP/143
Function: IMAP4 allows users to access and manage their email inbox from multiple devices, maintaining synchronization across all clients.

SMB – Server Message Block (Used in Microsoft Windows)

Ports:

• UDP/137 – NetBIOS name services (nbname)
• TCP/139 – NetBIOS session service (nbsession)
• TCP/445 – Direct SMB over TCP (without NetBIOS transport)
  Function: SMB enables file and printer sharing between computers. It is also known as CIFS (Common Internet File System).

SNMP – Simple Network Management Protocol

Ports: UDP/161 (Queries) & UDP/162 (Traps)
Function: SNMP is used for network device monitoring and management. It has different versions:

• v1: Basic, uses structured tables, data sent in plaintext.
• v2: Introduced bulk transfers and data type enhancements but remains insecure.
• v3: Secure standard with authentication and encryption.

LDAP – Lightweight Directory Access Protocol

Port: TCP/389
Function: LDAP is used to store and retrieve information in a network directory, commonly used for user authentication and directory services.

RDP – Remote Desktop Protocol

Port: TCP/3389
Function: RDP allows users to remotely access and control another computer, providing a full graphical desktop experience over a network.