N10-009 Networking Concepts Practice Question
At which layer of the OSI model does end-to-end communication and data segmentation occur?
⚠ Common exam trap
Many exam-takers confuse the transport layer's end-to-end communication with the network layer's end-to-end delivery of packets, forgetting that Layer 4 provides logical communication between processes (ports) while Layer 3 provides logical communication between hosts (IP addresses).
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 end-to-end communication between source and destination hosts, as well as data segmentation and reassembly. Protocols such as TCP and UDP operate at this layer, with TCP providing reliable, connection-oriented service by segmenting data into segments and managing flow control and error recovery.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Session layer
Why it's wrong here
The Session layer (Layer 5) is responsible for managing and synchronizing the dialogue between applications on different hosts. Its functions include establishing, maintaining, and terminating sessions, as well as providing synchronization points for data exchange. However, it relies entirely on the underlying Transport layer for the actual end-to-end data transfer and does not handle data segmentation or reliability mechanisms itself.
When this WOULD be correct
A question asking 'At which OSI layer does dialog control and session management occur?' would make the session layer correct.
- ✓
Transport layer
Why this is correct
The Transport layer is crucial for establishing logical end-to-end communication between specific application processes running on different hosts. It segments data from the Application layer, adding headers that include port numbers to identify these processes. This layer ensures reliable, ordered delivery via TCP, or provides faster, connectionless delivery with UDP, managing flow control and error recovery for the entire communication session between the two endpoints.
- ✗
Network layer
Why it's wrong here
The Network layer (Layer 3) primarily handles logical addressing (IP addresses) and routing packets across different networks to reach the destination host. While it ensures that data packets traverse the correct path through various routers, it does not manage the end-to-end communication between specific applications on those hosts. Its focus is on inter-network delivery, not the reliability or ordering of data streams for an application.
When this WOULD be correct
A question asking 'At which layer does routing and logical addressing occur?' would make the Network layer the correct answer.
- ✗
Data link layer
Why it's wrong here
The Data Link layer (Layer 2) manages node-to-node data transfer within the same local network segment. It frames data for physical transmission, uses MAC addresses for local device identification, and performs error detection on a hop-by-hop basis. This layer is concerned with reliable delivery between adjacent devices, such as a computer and a router, rather than the overarching end-to-end communication between two distant application processes.
When this WOULD be correct
In a question asking 'At which layer does error detection and correction using MAC addresses occur?' or 'Which layer is responsible for framing and media access control?', the data link layer would be correct.
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 is crucial for establishing logical end-to-end communication between specific application processes running on different hosts. It segments data from the Application layer, adding headers that include port numbers to identify these processes. This layer ensures reliable, ordered delivery via TCP, or provides faster, connectionless delivery with UDP, managing flow control and error recovery for the entire communication session between the two endpoints.
✗Session layerWrong answer — click to see why▾
Why this is wrong here
The session layer manages sessions (establish, maintain, terminate) but does not handle end-to-end communication or data segmentation; those are transport layer functions.
★ When this WOULD be the correct answer
A question asking 'At which OSI layer does dialog control and session management occur?' would make the session layer correct.
Why candidates choose this
Candidates confuse 'session' with 'connection' and think session layer manages end-to-end communication, not realizing that role belongs to the transport layer.
✗Network layerWrong answer — click to see why▾
Why this is wrong here
The Network layer (Layer 3) handles routing and logical addressing, not end-to-end communication and data segmentation, which are functions of the Transport layer.
★ When this WOULD be the correct answer
A question asking 'At which layer does routing and logical addressing occur?' would make the Network layer the correct answer.
Why candidates choose this
Candidates may confuse the Network layer's role in end-to-end delivery of packets with the Transport layer's end-to-end communication, or think segmentation happens at Layer 3 due to packet fragmentation.
✗Data link layerWrong answer — click to see why▾
Why this is wrong here
The data link layer handles node-to-node communication and framing, not end-to-end communication or data segmentation, which are functions of the transport layer.
★ When this WOULD be the correct answer
In a question asking 'At which layer does error detection and correction using MAC addresses occur?' or 'Which layer is responsible for framing and media access control?', the data link layer would be correct.
Why candidates choose this
Candidates may confuse the data link layer's role in local network delivery with end-to-end communication, or they might think segmentation occurs at a lower layer due to packet fragmentation at the network 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?”
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
Interior vs Exterior Routing Protocols
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.
Key term
Open Systems Interconnection
The Open Systems Interconnection (OSI) model is a conceptual framework used to understand how data travels from one computer to another across a network.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This N10-009 practice question is part of Courseiva's free CompTIA 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 N10-009 exam.