Telnet Protocol – A dedicated management tool

The Telnet protocol is applied over a TCP connection to send data in 8-bit encoded ASCII format, including Telnet verification sequences. Furthermore, this protocol is based on three basic concepts: the Virtual Network Terminal (NVT) paradigm, the principle of traded options, the trading rules. This is a base protocol, to which other protocols of the TCP / IP suite (FTP, SMTP, POP3, etc.) are applied. The specifications of this do not mention authentication because it is totally separate from the applications that use it. But, something we must know is that this is not a secure data transfer protocol, since the data it transmits circulates on the network as clear text (in an unencrypted way).

Data transmission via Telnet consists only of transmitting bytes in the TCP stream (the Telnet protocol specifies that data should be grouped by default – that is, if no option specifies otherwise – in a buffer before being sent. Specifically, this means that by default the data is sent line by line). When byte 255 is transmitted, the next byte should be interpreted as a command. Therefore, byte 255 is called IAC.

The Telnet protocol specifications allow taking into account the fact that certain terminals offer additional services, not defined in the basic specifications (but according to the specifications), in order to use advanced functions. These features are reflected as options. Therefore, the Telnet protocol provides an option negotiation system that allows the use of advanced functions in the form of options.

Currently the use of Telnet is practically limited to internal networks where there is a security shield that isolates the network from the outside. In all other cases, the SSH protocol is always used. The big problem with telnet is that the information from one terminal to another travels without any type of encryption, only in plain text. For a hacker, this information is extremely easy to obtain, if we take into account that both the username and the password to establish communication also comes as plain text, the security breach is brutal and that is why you should think twice before using this protocol.

Related reads:
IPv6 Protocol and how it replaces IPv4
HTTP or HyperText Transfer Protocol
FTP server on windows easy way to access

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