How are options negotiated in TELNET

How are options negotiated in TELNET?

The correct answer and explanation is :

In TELNET, options are negotiated using a process defined by the TELNET protocol, specifically using the negotiation process which operates through a series of control characters. The correct answer to how options are negotiated in TELNET is:

The client and server exchange IAC (Interpret As Command) sequences to negotiate options.

Explanation:

TELNET is a protocol used for remote communication over a network. It operates over the TCP/IP stack and enables clients to access remote servers. One key feature of TELNET is the ability to negotiate various options between the client (usually a user’s machine) and the server (the remote machine). These options can include terminal type, character set, and other features that both sides can agree to support.

The negotiation process is built around IAC (Interpret As Command) sequences. Here’s how it works in detail:

1. IAC Sequence: The control character IAC (byte value 255) is used to signal the start of a command in TELNET. This initiates an option negotiation. When either the client or server wants to negotiate an option, it sends an IAC followed by specific subcommands.
2. Option Commands: There are several option commands used in TELNET, including:

• WILL (code 251) – The sender of this command is indicating that it is willing to accept a particular option.
• WONT (code 252) – The sender indicates that it will not support a specific option.
• DO (code 253) – The sender requests that the recipient enable a particular option.
• DONT (code 254) – The sender requests that the recipient disable a particular option.

1. Exchange Process: The client and server exchange these IAC sequences to negotiate options. For example, the client may send IAC DO 1 (request to enable option 1), and the server may reply with IAC WILL 1 (indicating acceptance of the option). If either party does not support the option, they can respond with IAC DONT or IAC WONT.
2. Option Acknowledgment: After the negotiation of each option, both parties will acknowledge their agreement or disagreement by sending the appropriate response. If an option is successfully negotiated, it is activated, and further interaction can take place based on the negotiated parameters.

This negotiation mechanism allows for flexible communication and configuration between the client and the server, enabling them to support different features and capabilities throughout the session.

In summary, TELNET negotiates options using IAC sequences, where both the client and server exchange negotiation commands (WILL, WONT, DO, DONT) to enable or disable specific options as needed.