ISC2 CC Network Security Practice Question
A network administrator is troubleshooting connectivity issues and notices that frames are being dropped due to excessive collisions. Which OSI layer is most directly associated with this issue?
⚠ Common exam trap
The trap here is that candidates may associate 'dropped frames' with the Physical layer because collisions sound like a cabling/signal problem, but the exam expects recognition that collision handling is defined at the Data Link (MAC) sublayer.
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
✓
Data Link
Excessive collisions are a Layer 2 (Data Link) phenomenon because CSMA/CD and collision detection operate at the MAC sublayer of the Data Link layer. When two stations transmit simultaneously on a shared Ethernet segment, their frames collide, and the Data Link layer handles retransmission and backoff. The Physical layer deals with the electrical/optical signalling itself, not collision semantics.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Physical
Why it's wrong here
Collisions arise from CSMA/CD media-access contention, which the data-link layer governs, so the fault sits at layer 2, not layer 1. Physical covers cabling, connectors, voltages and signal encoding; it would be the answer for attenuation, crosstalk or duplex mismatch symptoms.
- ✓
Data Link
Why this is correct
Collisions occur when devices on a shared medium transmit simultaneously; Ethernet's CSMA/CD and frame delivery operate at the Data Link layer, so excessive collisions and dropped frames are diagnosed there. Layer 1 handles raw signalling, not collision handling.
- ✗
Network
Why it's wrong here
Layer 3 routes packets between networks and handles logical addressing; collision-induced frame drops occur below it, where shared media access is arbitrated. It is tempting because connectivity faults often implicate routing, but routers forward frames only after Layer 2 has resolved contention, so excessive collisions are not a Network layer symptom.
- ✗
Transport
Why it's wrong here
Layer 4 manages end-to-end segments, ports and reliability; collisions occur on the physical medium before any segment is built. It is tempting because dropped frames disrupt transport sessions, but TCP or UDP never detect collisions themselves — the NIC and MAC sublayer do, so Transport is not the associated layer.
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
Go deeper
Related to this question
Learn chapter
Network Security Components and Controls
Key term
Detection
Detection is the process of identifying potential security incidents or anomalies by analyzing system data, logs, and network traffic.
Key term
MAC
MAC (Media Access Control) is a unique hardware identifier assigned to network interfaces for communication on a local network segment.
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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.