ISC2 CC Network Security Practice Question
A security analyst is reviewing network traffic and notices that some devices are using a protocol that does not guarantee delivery and has no error recovery. Which ONE transport layer protocol fits this description? (Select ONE)
⚠ Common exam trap
The trap is confusing transport layer protocols with application or network layer protocols. Candidates might choose HTTP because it is common, but HTTP is application layer and relies on TCP. Also, some might think ICMP is transport layer because it is connectionless, but it is network layer. The key is to remember that UDP is the only transport layer protocol among the options that lacks reliability guarantees.
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
✓
UDP
UDP (User Datagram Protocol) is a connectionless transport layer protocol that does not guarantee delivery, ordering, or error recovery. It is designed for speed and low overhead, making it suitable for applications like streaming, DNS, and VoIP where occasional packet loss is acceptable. The question explicitly asks for a protocol that does not guarantee delivery and has no error recovery, which matches UDP's characteristics.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
TCP
Why it's wrong here
TCP provides connection-oriented delivery with acknowledgements, retransmission and sequencing, so it guarantees delivery and performs error recovery. It is tempting because TCP is the dominant transport protocol, but its reliability mechanisms directly contradict the scenario's requirement for a protocol with neither guarantee nor recovery.
- ✗
HTTP
Why it's wrong here
HTTP is an application-layer protocol that runs over TCP, which does guarantee delivery and error recovery; it does not fit the description. HTTP is tempting because it is ubiquitous in traffic analysis, but the transport-layer protocol lacking delivery guarantees and error recovery is UDP.
- ✗
ICMP
Why it's wrong here
ICMP sits at the network layer, not the transport layer, so it cannot be the protocol the question asks for. It is tempting because ICMP also lacks delivery guarantees and error recovery, but those traits belong to connectionless transport protocols such as UDP, not to a diagnostic messaging protocol.
- ✓
UDP
Why this is correct
UDP is connectionless and provides no acknowledgement, retransmission or sequencing, so delivery is never guaranteed and lost datagrams are not recovered. This directly satisfies the stem's constraint of a transport protocol lacking both guaranteed delivery and error recovery, unlike TCP, which retransmits unacknowledged segments.
- ✗
ARP
Why it's wrong here
ARP operates at the data link layer, resolving IP addresses to MAC addresses, and is not a transport-layer protocol at all. ARP is tempting because it appears in packet captures alongside IP traffic, but the transport-layer protocol with no delivery guarantee or error recovery is UDP.
Go deeper
Related to this question
Learn chapter
Business Continuity and Disaster Recovery
Key term
User
A user is any person, system, or device that interacts with an IT service, resource, or identity system, typically authenticated through credentials and authorized to perform specific actions.
Key term
DNS
DNS is the system that translates human-friendly domain names like example.com into machine-readable IP addresses so computers can find each other on a network.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official ISC2 exam blueprint
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.