Protocol stack usage: when using Telnet or FTP, what is the highest OSI layer involved in transmitting your application data?

Introduction / Context:
Telnet and FTP are classic application-layer protocols. When describing “the highest layer you are using,” we refer to where the user-level protocol logic resides, not merely the underlying transport or presentation encoding.

Given Data / Assumptions:

• Telnet provides remote terminal access; FTP provides file transfer.
• OSI layers above Transport are Session, Presentation, and Application.
• In most practical mappings, application protocols are said to operate at the Application layer, while Presentation/Session services are either minimal or absorbed by the application in TCP/IP.

Concept / Approach:
Determine the layer that defines the semantics and commands of Telnet and FTP (for example, FTP commands like USER, PASS, GET). Those belong to the Application layer. The underlying reliability comes from Transport (TCP), but the “highest” layer in use is Application.

Step-by-Step Solution:

Verification / Alternative check:
IANA assigns application ports (Telnet 23, FTP 21) and RFCs define application commands; this is definitive evidence of Application-layer operation.

Why Other Options Are Wrong:
Presentation/Session: Often collapsed into Application in TCP/IP stacks and not singled out for Telnet/FTP specifically.
Transport: Provides delivery but not the application semantics.

Common Pitfalls:
Confusing “uses TCP” with “Transport layer is the highest.” The highest layer involved by the application remains Application.

Final Answer:
Application