SSH, Telnet and Rlogin are network protocols that allow you to log into a multi-user PC from another computer, over a network.From your PC, you can run a client to make a network connection to the other computer (the server). The network connection carries your keystrokes and commands from the client to the server, and carries the server’s responses back to you.
Operating systems like Unix have a command-line interface similar to ‘Command Prompt’ or ‘MS-DOS Prompt’ in Windows. The system prints a prompt, where you can type commands for the system to execute.SSH, Telnet or Rlogin are very useful when you want to access a unix or linux server from your PC.
Unlike Unix, computers running windows operating system, have their own ways of networking among themselves, and you may not find the need to use any of these remote login protocols.
How do SSH, Telnet and Rlogin differ?
- SSH stands for ‘secure shell’ and it is a relatively new high-security protocol. It uses strong cryptography to protect your connection against eavesdropping, hijacking and other attacks. Telnet and Rlogin are both older protocols offering minimal security.
- Both SSH and Rlogin allow you to log in to the server without having to type a password. However Rlogin’s method of doing this is insecure, and can allow an attacker to access your account on the server. SSH’s method is much more secure, and breaking it requires the hacker to gain access to your PC (client machine).
- SSH allows you to connect to the server and automatically send a command, so that the server will run that command and then disconnect. So you can use it in automated processing.
While it is advisable to use SSH if you are connecting to the server across the open Internet, you can use Telnet or Rlogin only if your client and server are both behind a good firewall.