- A
Application layer
Why wrong: The Application layer (Layer 7) provides network services to applications (e.g., HTTP). It does not add transport headers; it passes data to the Transport layer.
- B
Presentation layer
Why wrong: The Presentation layer (Layer 6) handles data formatting, encryption, and compression. It does not add TCP segment headers.
- C
Session layer
Why wrong: The Session layer (Layer 5) manages sessions between applications. It does not add transport headers; that is the role of the Transport layer.
- D
Transport layer
The Transport layer (Layer 4) takes data from upper layers, segments it, and adds a TCP or UDP header. For HTTP, the TCP segment header is added at this layer.
Question 250 of 520
N10-009 Networking Concepts Practice Question
This N10-009 practice question tests your understanding of networking concepts. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network technician is reviewing the OSI model to understand how data is encapsulated when a web request is sent from a client to a server. At which layer does the web browser's HTTP request data get encapsulated with a TCP segment header?
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
✓
Transport layer
The Transport layer (Layer 4) is responsible for encapsulating application data with a TCP or UDP segment header. When a web browser sends an HTTP request, the HTTP data is passed down from the Application layer to the Transport layer, where the TCP segment header (including source/destination ports, sequence numbers, and checksum) is added. This encapsulation occurs at Layer 4, not at any higher layer.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Application layer
Why it's wrong here
The Application layer (Layer 7) provides network services to applications (e.g., HTTP). It does not add transport headers; it passes data to the Transport layer.
When this WOULD be correct
This option would be correct if the question asked: 'At which layer does the web browser's HTTP request data originate or get created?' or 'At which layer does the HTTP protocol operate?'
- ✗
Presentation layer
Why it's wrong here
The Presentation layer (Layer 6) handles data formatting, encryption, and compression. It does not add TCP segment headers.
When this WOULD be correct
A question asking at which layer data encryption (e.g., TLS) occurs during a secure web request would have the Presentation layer as the correct answer, as it handles encryption services.
- ✗
Session layer
Why it's wrong here
The Session layer (Layer 5) manages sessions between applications. It does not add transport headers; that is the role of the Transport layer.
When this WOULD be correct
A question asking: 'At which OSI layer does a protocol establish, maintain, and terminate a communication session between two applications?' would make Session layer the correct answer.
- ✓
Transport layer
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 N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓Transport layerCorrect answer▾
Why this is correct
The Transport layer (Layer 4) takes data from upper layers, segments it, and adds a TCP or UDP header. For HTTP, the TCP segment header is added at this layer.
✗Application layerWrong answer — click to see why▾
Why this is wrong here
HTTP operates at the Application layer (Layer 7), but the TCP segment header is added at the Transport layer (Layer 4) during encapsulation. The question specifically asks where the HTTP data gets encapsulated with a TCP segment header, which occurs at the Transport layer, not the Application layer.
★ When this WOULD be the correct answer
This option would be correct if the question asked: 'At which layer does the web browser's HTTP request data originate or get created?' or 'At which layer does the HTTP protocol operate?'
Why candidates choose this
Candidates often confuse the layer where a protocol operates with the layer where its data is encapsulated by the next lower layer. Since HTTP is an application-layer protocol, they mistakenly think the HTTP data is encapsulated at the Application layer.
✗Presentation layerWrong answer — click to see why▾
Why this is wrong here
The Presentation layer (Layer 6) handles data translation, encryption, and compression, not encapsulation with TCP segment headers. TCP segment headers are added at the Transport layer (Layer 4).
★ When this WOULD be the correct answer
A question asking at which layer data encryption (e.g., TLS) occurs during a secure web request would have the Presentation layer as the correct answer, as it handles encryption services.
Why candidates choose this
Candidates may confuse the Presentation layer's role in formatting data for the application with the Transport layer's role in segmenting and adding headers, especially when thinking about HTTP data being prepared for transmission.
✗Session layerWrong answer — click to see why▾
Why this is wrong here
The Session layer (Layer 5) manages sessions, not encapsulation of data into segments; TCP segment headers are added at the Transport layer (Layer 4).
★ When this WOULD be the correct answer
A question asking: 'At which OSI layer does a protocol establish, maintain, and terminate a communication session between two applications?' would make Session layer the correct answer.
Why candidates choose this
Candidates may confuse the Session layer's role in managing dialogue control with the encapsulation process, or think that HTTP (an application protocol) is directly encapsulated at a higher layer.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the Application layer (where HTTP data is generated) with the layer where the TCP header is added, mistakenly thinking encapsulation happens at Layer 7 instead of Layer 4.
Detailed technical explanation
How to think about this question
Under the hood, the TCP segment header includes fields such as source port (e.g., ephemeral port 49152-65535), destination port (e.g., 80 or 443), sequence number, acknowledgment number, and a 16-bit checksum for error detection. In a real-world scenario, if a firewall is inspecting traffic at Layer 4, it examines the TCP header to allow or deny the segment based on port numbers, while the HTTP payload remains untouched until it reaches the Application layer on the server.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the N10-009 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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 |
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this N10-009 question test?
Networking Concepts — This question tests Networking Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Transport layer — The Transport layer (Layer 4) is responsible for encapsulating application data with a TCP or UDP segment header. When a web browser sends an HTTP request, the HTTP data is passed down from the Application layer to the Transport layer, where the TCP segment header (including source/destination ports, sequence numbers, and checksum) is added. This encapsulation occurs at Layer 4, not at any higher layer.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jun 11, 2026
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