Which TCP/IP sub-protocol operates at Layer4 of the OSI model?

UDP is a core TCP/IP sub-protocol that operates at Layer 4 (the Transport Layer) of the OSI model, responsible for connectionless data delivery between applications.

Submitted by mike_84· Apr 18, 2026

Question

Options

AHTTPS
BFTP
CUDP
DSSH

Why each option

UDP is a core TCP/IP sub-protocol that operates at Layer 4 (the Transport Layer) of the OSI model, responsible for connectionless data delivery between applications.

AHTTPS

HTTPS (Hypertext Transfer Protocol Secure) operates at Layer 7 (Application Layer) and uses TCP for its underlying transport.

BFTP

FTP (File Transfer Protocol) operates at Layer 7 (Application Layer) and relies on TCP for reliable data transfer.

CUDP

DSSH

SSH (Secure Shell) operates at Layer 7 (Application Layer) and uses TCP to establish a secure channel for remote access.

Concept tested: OSI model layers (Transport Layer protocols)

Source: https://learn.microsoft.com/en-us/windows/win32/winsock/the-osi-model-and-tcp-ip-protocol-suite

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