Question

Which of the following protocols operate at the Transport Layer of the OSI Model?

• A. HTTP and FTP
• B. TCP and UDP
• C. ARP and RARP
• D. IP and ICMP

Hint:

Layer 4 uses port numbers for process-to-process delivery. Which pair is reliable plus lightweight?

Answer 1

The Correct Option is B

Step 1: Ask which protocols use port numbers to deliver data to a specific process. That is the signature of Layer 4.

Step 2: HTTP and FTP ride on top of a transport protocol, IP and ICMP route packets between hosts, and ARP and RARP resolve hardware addresses. None of these carry port-based end-to-end delivery.

Step 3: The pair that provides port-addressed transport, one reliable and one lightweight, is TCP and UDP.

\[ \boxed{\text{TCP and UDP}} \]