In computer networking, what is TELNET and what is its primary purpose when used over a TCP/IP network?

Introduction / Context:
TELNET is one of the earliest application layer protocols defined for TCP/IP networks. Although it has largely been replaced by secure alternatives such as SSH, it remains a key concept in networking courses and interviews. Understanding TELNET helps you appreciate how remote login and terminal emulation were originally implemented across the internet.

Given Data / Assumptions:

• We are working in the context of TCP/IP networks.
• TELNET operates at the application layer.
• Users need to remotely access a command-line environment on another host.
• Security improvements like encryption are not built into the basic TELNET protocol.

Concept / Approach:
TELNET is a terminal emulation protocol that runs over TCP, typically on port 23. It allows a user on one system to establish a text-based remote session to another system and interact with it as if they were using a local terminal. The protocol sends keystrokes and receives output in clear text. Although this lack of encryption is a major security disadvantage today, the functional idea of remote command execution remains the same and is now more safely achieved with SSH.

Step-by-Step Solution:
1. Identify the main function of TELNET: remote text-based login and command execution.2. Remember that TELNET is not designed for file transfer, routing, or Wi-Fi security; it is focused on terminal emulation.3. Option A states that TELNET is a terminal emulation protocol that allows users to log in remotely to another host and run commands over a TCP/IP connection, which matches the standard definition.4. Option B confuses TELNET with file transfer protocols like FTP or SFTP.5. Option C mislabels TELNET as a routing protocol; in reality, routing protocols include RIP, OSPF, and BGP.6. Option D incorrectly describes TELNET as a Wi-Fi encryption standard; wireless encryption uses mechanisms such as WPA2 and WPA3.7. Therefore, Option A is the correct answer.

Verification / Alternative check:
If you install a TELNET client and connect to a TELNET server, you will see a remote command-line prompt where you can type commands. No graphical windows or file transfer interface appears; instead, the experience resembles using a basic text terminal. Documentation for TELNET consistently describes it as a terminal emulation and remote login protocol, confirming the explanation in Option A.

Why Other Options Are Wrong:
Option B is wrong because dedicated file transfer protocols such as FTP and SCP serve that role, not TELNET.Option C is wrong because TELNET does not participate in routing table exchanges.Option D is wrong because TELNET traffic itself is unencrypted and should not be confused with security standards.

Common Pitfalls:
Many learners underestimate the security risk of TELNET, forgetting that all credentials and data are transmitted in clear text. In modern environments, TELNET is usually disabled or restricted, and SSH is used instead. However, the conceptual knowledge of TELNET is still valuable for understanding the historical development of network services and for interpreting legacy systems or exam questions.

Final Answer:
TELNET is a terminal emulation protocol that allows users to log in remotely to another host and run commands over a TCP/IP connection.