ISC2 CC Network Security Practice Question
Which two protocols operate at the Transport layer of the OSI model? (Choose TWO.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
TCP
TCP and UDP are the primary Transport layer protocols. IP is Network layer, Ethernet is Data Link, and HTTP is Application layer.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
HTTP
Why it's wrong here
HTTP operates at the Application layer, defining request and response semantics for web resources, so it cannot satisfy a Transport layer requirement. It is tempting because HTTP runs directly over TCP and its traffic dominates networks, but the protocol itself sits above the Transport layer in the OSI stack.
- ✓
TCP
Why this is correct
TCP operates at the Transport layer, providing connection-oriented, reliable delivery with sequencing, acknowledgements and flow control. Its layer 4 port addressing and segmentation satisfy the question's requirement for protocols operating at the Transport layer of the OSI model.
- ✗
IP
Why it's wrong here
IP operates at the Network layer, handling logical addressing and routing between networks, so it cannot satisfy a Transport layer requirement. It is tempting because IP is connectionless and carries port numbers in its header, but those ports belong to TCP and UDP, which are the actual Transport layer protocols.
- ✗
Ethernet
Why it's wrong here
Ethernet operates at the Data Link layer, framing packets and addressing them by MAC address on the local segment, so it fails a Transport layer requirement. It is tempting because Ethernet is the ubiquitous transport medium beneath TCP/IP, yet that physical carriage role is distinct from Transport layer end-to-end delivery.
- ✓
UDP
Why this is correct
UDP is a Transport layer protocol, providing connectionless datagram delivery with port addressing and optional checksums. It sits at layer 4 alongside TCP, satisfying the question's requirement for protocols operating at the Transport layer of the OSI model.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CC practice question is part of Courseiva's free ISC2 certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CC exam.