CCNA Network Infrastructure and Connectivity Practice Question
Which two statements accurately describe UDP compared with TCP?
⚠ Common exam trap
Be careful not to confuse the connection-oriented features of TCP with UDP, which is connectionless and does not guarantee delivery.
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 is connectionless.
UDP is designed for simplicity and speed rather than built-in reliability. In plain terms, it sends data without creating a formal conversation first. That is why it is called connectionless. Because it does not perform the same reliability features as TCP, its header is smaller and the protocol adds less overhead. This makes UDP a good fit for applications that care more about speed or low delay than guaranteed delivery at the transport layer. UDP does not perform a three-way handshake, and it does not guarantee delivery. It is also used by many real services, including DNS in common query scenarios.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
UDP is connectionless.
Why this is correct
UDP is connectionless, meaning it treats each datagram independently and does not establish a persistent logical link before sending data. There is no initial handshake, and the sender does not maintain state about the receiver. This allows immediate transmission of application data without negotiation, which is essential for low-latency protocols like streaming or real-time communications.
- ✗
UDP always guarantees delivery and sequencing.
Why it's wrong here
UDP does not guarantee delivery, ordering, or duplicate protection, so this statement is false. It lacks sequence numbers and acknowledgments, so packets can be lost, duplicated, or arrive out of order without detection or correction. Reliable delivery and in-order sequencing are TCP services, achieved through sequence numbers, ACKs, and retransmissions.
When this WOULD be correct
In a question focused on the characteristics of a reliable transport protocol, such as 'Which protocol guarantees delivery and sequencing of packets?' the correct answer would be B, as it would accurately describe TCP's features.
- ✓
UDP has lower overhead because it uses a simpler header and no session establishment.
Why this is correct
UDP incurs lower overhead than TCP because its fixed 8-byte header is far smaller than TCP's 20-byte minimum, and it omits mechanisms like connection tracking, sequence numbers, acknowledgments, and retransmission. Since no session establishment or teardown is required, UDP avoids the additional round trips and processing that TCP spends on opening and closing connections. This makes UDP more efficient for lightweight request-response and real-time traffic.
- ✗
UDP requires a three-way handshake before application data can be sent.
Why it's wrong here
No three-way handshake occurs in UDP, so this statement is false. The three-way handshake (SYN, SYN-ACK, ACK) is a TCP connection-establishment mechanism used to synchronize sequence numbers and negotiate parameters before data transfer. UDP simply creates a socket at each end and sends datagrams immediately, with no preliminary negotiation.
When this WOULD be correct
If the exam question asked about a protocol that does require a connection establishment, such as TCP, or if it specifically inquired about the differences in connection-oriented versus connectionless protocols, then this option would be correct.
- ✗
UDP cannot be used by DNS.
Why it's wrong here
DNS absolutely uses UDP, making this statement false. Standard DNS queries and responses are sent over UDP port 53 because UDP's low overhead and speed perfectly suit the small, single-packet exchange that typical lookups require. TCP is reserved for exceptional cases like large responses or zone transfers, but the default transport for normal DNS operation is UDP.
When this WOULD be correct
If the exam question stated that UDP cannot be used for certain protocols or applications, such as those requiring guaranteed delivery, then this option would be correct. For example, a question could ask which protocols are incompatible with UDP in scenarios requiring reliable communication.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓UDP is connectionless.Correct answer▾
Why this is correct
UDP is connectionless, meaning it treats each datagram independently and does not establish a persistent logical link before sending data. There is no initial handshake, and the sender does not maintain state about the receiver. This allows immediate transmission of application data without negotiation, which is essential for low-latency protocols like streaming or real-time communications.
✗UDP always guarantees delivery and sequencing.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because UDP does not guarantee delivery or sequencing; it is designed for speed and efficiency, sacrificing reliability. TCP, on the other hand, ensures that data is delivered in order and without loss.
★ When this WOULD be the correct answer
In a question focused on the characteristics of a reliable transport protocol, such as 'Which protocol guarantees delivery and sequencing of packets?' the correct answer would be B, as it would accurately describe TCP's features.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of UDP's functionality, conflating it with TCP's reliability features, which can lead to confusion about the fundamental differences between the two protocols.
✗UDP requires a three-way handshake before application data can be sent.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because UDP is a connectionless protocol that does not require a three-way handshake for data transmission, unlike TCP, which establishes a connection before sending data.
★ When this WOULD be the correct answer
If the exam question asked about a protocol that does require a connection establishment, such as TCP, or if it specifically inquired about the differences in connection-oriented versus connectionless protocols, then this option would be correct.
Why candidates choose this
Candidates may choose this option due to confusion between the connection-oriented nature of TCP and the connectionless nature of UDP, leading them to mistakenly believe that all protocols require a handshake.
✗UDP cannot be used by DNS.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because UDP is widely used by DNS for its quick query-response nature, allowing for faster resolution of domain names without the overhead of connection establishment.
★ When this WOULD be the correct answer
If the exam question stated that UDP cannot be used for certain protocols or applications, such as those requiring guaranteed delivery, then this option would be correct. For example, a question could ask which protocols are incompatible with UDP in scenarios requiring reliable communication.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of UDP's capabilities, mistakenly believing that all network services require guaranteed delivery, thus overlooking DNS's specific use of UDP.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
Quick reference
OSI Model Reference
| Layer | Name | PDU | Key Protocols / Devices |
|---|---|---|---|
| 7 | Application | Data | HTTP, HTTPS, DNS, SMTP, FTP, SSH |
| 6 | Presentation | Data | TLS / SSL, JPEG, ASCII encoding |
| 5 | Session | Data | NetBIOS, RPC, SIP |
| 4 | Transport | Segment / Datagram | TCP, UDP |
| 3 | Network | Packet | IP, ICMP, OSPF — Routers |
| 2 | Data Link | Frame | Ethernet, Wi-Fi, PPP — Switches, Bridges |
| 1 | Physical | Bits | Cables, NICs, Hubs, Repeaters |
Go deeper
Related to this question
Learn chapter
TCP Three-Way Handshake
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.
Key term
UDP
UDP (User Datagram Protocol) is a communication protocol that sends data quickly without first checking if the receiver is ready or if the data arrived correctly.
About these practice questions
This 200-301 question is part of Courseiva's 1,389-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco 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 200-301 exam.