Network Protocol: TELNET, SSH

TELNET

Telnet is a network protocol that provides a command-line interface for communication with a remote device or server over a network.

Telnet allows users to connect to remote computers or devices over the Internet or a local network to manage and control them.

Through Telnet, users can execute commands on the remote system as if they were physically present at the console of that machine.

 Example Scenario: Accessing a Remote Server via Telnet

1. Setup:

   • You have a remote server with the IP address 192.168.1.100.
   • Telnet service is running on this server.
   • You have a Telnet client installed on your local machine.

2. Connecting to the Remote Server:

• Open a command prompt (Windows) or terminal (Linux/Mac) on your local machine.
• Type the command to initiate a Telnet connection to the remote server:

  Command: telnet 192.168.1.100

Note: No Encryption in TELNET: Telnet transmits all data, including passwords and commands, in plaintext. This makes it vulnerable.

Port: TELNET typically uses TCP port 23 for communication between the client and the server.

SSH

SSH stands for Secure Shell. It is a cryptographic network protocol that allows secure communication between two computers over an insecure network. SSH is widely used for securely accessing and managing remote servers and devices, providing a secure command-line interface (CLI) and enabling secure file transfers.

It is just like Telnet which allow the user to connect to a remote server over a network but difference is that it encrypts all the data exchanged between the client and server.

Port: SSH typically uses TCP port 22 for communication between the client and the server.

Example: Connecting to a remote server

• Open a terminal or SSH client application.
• Use the ssh command followed by the username and IP address (or hostname) of the SSH server you want to connect to: Command: ssh username@server_ip_address    

RDP

RDP stands for Remote Desktop Protocol. It is a proprietary protocol developed by Microsoft that allows a user to connect to and control a remote computer over a network connection.

RDP enables users to remotely access and control a Windows-based computer or server from another device.  

It provides a graphical interface, allowing users to see and interact with the remote desktop as if they were sitting in front of it. This includes accessing applications, files, and performing administrative tasks.

RDP sessions are encrypted using various encryption protocols (e.g., TLS), ensuring secure communication between the client and the remote server.

Port: RDP typically uses TCP port 3389 for communication between the client and the server.