Telnet and SSH are the general purpose client server application program and uses remote terminal service which allows a user at one site to interact with a remote time-sharing system at another site as if the user’s keyboard and a display connected directly to the remote machine.
The main difference between Telnet and SSH is that the Telnet is conventional protocol whereas SSH is the replacement for Telnet protocol and also SSH have enhanced features.
Content: Telnet Vs SSH
|Basis for comparison||Telnet||SSH|
|Security||Less secured||Highly secured|
|Uses port number||23||22|
|Data format||Telnet sends the data in plain text.||Encrypted format is used to send data and also uses a secure channel.|
|Authentication||No privileges are provided for users authentication.||Uses public key encryption for authentication.|
|Suitability of network||Private networks are recommended.||Suitable for Public networks.|
|Vulnerabilities||Vulnerable to security attacks.||SSH has overcome many security issues of telnet.|
Definition of Telnet
TELNET is the general-purpose client-server program that lets you access any application program on a remote computer. It works like, a user can use the services available on the remote computer and transfer the results back to the local computer. TELNET is an abbreviation for TErminal NETwork. TELNET facilitates the establishment of the connection to a remote system in a manner that the local terminal resembles to be a terminal at the remote system.
Whenever a user intends to access an application program or utility placed on a remote machine, then user performs Remote Login. Here the TELNET client server program is utilized. The user sends the keystrokes to the terminal driver, and the local operating system accepts the characters however characters are not interpreted. The characters are sent to TELNET client and transformed into a universal character set referred to as Network Virtual Terminal characters. Then these characters are delivered to the local TCP/IP stack.
The text and commands in NVT form travel through the internet and arrives at the TCP/IP stack at the remote machine. Here the characters are delivered to the operating system and passed to TELNET server, which changes the characters to the corresponding understandable characters interpreted by the remote computer. The characters are passed to the terminal driver as it is not designed to receive characters from a TELNET server. The solution is to add a piece of software called a pseudo terminal driver which behaves as the characters are transmitted from the terminal. At last, the operating system passes the characters to the appropriate application program.
Although TELNET is widely used and is not as sophisticated as some remote terminal protocols. Usually, TELNET client software allows the user to specify a remote machine either by the giving its domain name or IP address.
The three type of basic services that TELNET offers are:
1. It defines a virtual network terminal that provides a standard interface to remote systems.
2. It provides a set of standard options and includes a mechanism that allows the client and server to negotiate options.
3. It allows an arbitrary program to become a client or either end can negotiate options.
Definition of SSH
SSH (Secure SHell) is a network protocol which provides a replacement for insecure remote login and command execution facilities, such as telnet, rlogin and rsh. It encrypts traffic in both directions, preventing traffic, sniffing and password theft. SSH also offers several additional useful features like compression, public key authentication, Authentication of the server, port forwarding, X11 forwarding, file transfer.
SSH also supports remote command execution. When you log in, a pseudo-terminal is assigned to your session and your session, will remain open until you explicitly log out or is terminated from the server end. This protocol provides functionalities like Secure command-shell, secure file transfer and port forwarding.
- Secure Command Shell: It allows a user to view the contents of directories, edit files and access custom database applications remotely.
- Secure file transfer: It is act as a subsystem of the secure shell protocol. Essentially, Secure file transfer protocol is a separate protocol layered over the SSH protocol to handle the transfer of a file.
- Port forwarding: It is also known as tunnelling, which provides the basic security for the TCP/IP application.
Key Differences Between Telnet and SSH
- Telnet and SSH both serve the same purpose and provides the connectivity to the remote server but Telnet is conventional protocol, although it is still in use in the various application. SSH is the replacement for Telnet and has some enhanced features too.
- Telnet doesn’t provide any security mechanism whereas SSH is more secure and provides security measures.
- In Telnet transmits data in plain text that is the reason it is vulnerable to security attacks. On the other hand, SSH uses encryption for transmitted data and security breach does not likely occur. SSH can withstand eavesdropping, man in the middle and insertion/ replay attacks.
- Telnet doesn’t provide authentication facility while SSH provides user authentication.
- Telnet works with a private network. In contrast, SSH works with a public network.
- Telnet communicates via port number 23 over TCP/IP. As against, SSH uses port number 22 for communication.
The SSH protocol is a somewhat better replacement for Telnet as SSH has security measures. While Telnet does not provide much security although still in use.