Domain 1.1: Explain concepts related to the Open Systems Interconnection (OSI) reference model Flashcards

1
Q

Question: What is the primary function of Layer 1 in the OSI model?
Answer Options:
A. Error detection and correction
B. Establishing and maintaining connections
C. Transmission of raw data over physical media
D. Routing data between networks

A

Correct Answer + Explanation:
Layer 1, the Physical layer, is responsible for transmitting raw data over physical media like cables and wireless signals.
Practical Use:
Examples include Ethernet cables, fiber optics, and wireless signals.
Why Others Are Incorrect:
A: Error detection happens at the Data Link layer.
B: Connection management occurs in the Session layer.
D: Routing is handled by the Network layer.
Exam Objective Reference:
Domain 1.1: OSI Model - Physical Layer.
Follow-Up:
What devices operate primarily at Layer 1?

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2
Q

Question: Which layer of the OSI model is responsible for IP addressing and packet routing?
Answer Options:
A. Data Link
B. Network
C. Transport
D. Physical

A

Correct Answer + Explanation:
The Network layer handles IP addressing, routing, and forwarding data packets between networks.
Practical Use:
Routers operate at Layer 3 to determine the best path for data.
Why Others Are Incorrect:
A: Data Link deals with MAC addresses and frames.
C: Transport manages end-to-end communication.
D: Physical is for transmitting raw data.
Exam Objective Reference:
Domain 1.1: OSI Model - Network Layer.
Follow-Up:
What is the main protocol used at the Network layer?

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3
Q

Question: At which OSI layer does error detection and correction occur?
Answer Options:
A. Application
B. Data Link
C. Transport
D. Network

A

Correct Answer + Explanation:
The Data Link layer handles error detection and correction for frames during transmission.
Practical Use:
Switches and NICs work at this layer.
Why Others Are Incorrect:
A: Application deals with user interfaces.
C: Transport focuses on data segmentation and reassembly.
D: Network manages routing and IP addressing.
Exam Objective Reference:
Domain 1.1: OSI Model - Data Link Layer.
Follow-Up:
What is the name of the addressing system used at the Data Link layer?

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4
Q

Question: Which layer of the OSI model is responsible for ensuring data is delivered error-free and in the correct sequence?
Answer Options:
A. Presentation
B. Transport
C. Network
D. Session

A

Correct Answer + Explanation:
The Transport layer ensures reliable delivery of data using error correction and sequencing.
Practical Use:
TCP is a key protocol at this layer.
Why Others Are Incorrect:
A: Presentation handles data formatting.
C: Network is for routing.
D: Session establishes and manages sessions.
Exam Objective Reference:
Domain 1.1: OSI Model - Transport Layer.
Follow-Up:
Which Transport layer protocol provides connectionless communication?

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5
Q

Question: Which OSI layer is responsible for translating data into a format suitable for application processes?
Answer Options:
A. Application
B. Presentation
C. Transport
D. Session

A

Correct Answer + Explanation:
The Presentation layer ensures data is in a usable format for applications by handling encryption, compression, and translation.
Practical Use:
Encryption protocols like SSL/TLS operate here.
Why Others Are Incorrect:
A: Application provides user interfaces.
C: Transport ensures data reliability.
D: Session manages connections.
Exam Objective Reference:
Domain 1.1: OSI Model - Presentation Layer.
Follow-Up:
What is an example of a format conversion handled by the Presentation layer?

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6
Q

Question: What is the primary role of the Session layer in the OSI model?
Answer Options:
A. Error detection
B. Managing and maintaining connections between applications
C. Translating data formats
D. Routing packets

A

Correct Answer + Explanation:
The Session layer is responsible for establishing, managing, and terminating communication sessions between applications.
Practical Use:
Video conferencing applications rely on this layer to manage sessions.
Why Others Are Incorrect:
A: Error detection is a Data Link responsibility.
C: Translation occurs in the Presentation layer.
D: Routing is done at the Network layer.
Exam Objective Reference:
Domain 1.1: OSI Model - Session Layer.
Follow-Up:
What are examples of protocols used at the Session layer?

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7
Q

Question: Which OSI layer directly interacts with end-user applications?
Answer Options:
A. Presentation
B. Application
C. Transport
D. Session

A

Correct Answer + Explanation:
The Application layer provides an interface for user applications to access network services.
Practical Use:
Web browsers and email clients use protocols like HTTP and SMTP at this layer.
Why Others Are Incorrect:
A: Presentation handles data formatting.
C: Transport manages reliability.
D: Session manages connections.
Exam Objective Reference:
Domain 1.1: OSI Model - Application Layer.
Follow-Up:
What protocols operate at the Application layer?

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8
Q

Question: At which OSI layer does MAC addressing occur?
Answer Options:
A. Physical
B. Data Link
C. Network
D. Transport

A

Correct Answer + Explanation:
The Data Link layer is responsible for MAC addressing, enabling devices on the same network to communicate.
Practical Use:
Switches use MAC addresses to forward frames.
Why Others Are Incorrect:
A: Physical layer handles transmission media.
C: Network uses IP addresses.
D: Transport ensures reliable communication.
Exam Objective Reference:
Domain 1.1: OSI Model - Data Link Layer.
Follow-Up:
How does a MAC address differ from an IP address?

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9
Q

Question: What is a PDU (Protocol Data Unit) called at the Transport layer?
Answer Options:
A. Frame
B. Packet
C. Segment
D. Data

A

Correct Answer + Explanation:
At the Transport layer, the PDU is called a segment, which includes data and Transport layer headers.
Practical Use:
TCP and UDP create segments to manage data delivery.
Why Others Are Incorrect:
A: Frames belong to the Data Link layer.
B: Packets are for the Network layer.
D: Data is a generic term used at higher layers.
Exam Objective Reference:
Domain 1.1: OSI Model - Transport Layer.
Follow-Up:
What is the PDU called at the Network layer?

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10
Q

Question: Which OSI layer deals with the electrical, optical, or radio signals used to transmit data?
Answer Options:
A. Physical
B. Data Link
C. Network
D. Transport

A

Correct Answer + Explanation:
The Physical layer handles signal transmission and defines hardware specifications.
Practical Use:
Fiber optics, coaxial cables, and wireless standards like 802.11 are examples.
Why Others Are Incorrect:
B: Data Link handles framing.
C: Network manages IP routing.
D: Transport ensures reliable delivery.
Exam Objective Reference:
Domain 1.1: OSI Model - Physical Layer.
Follow-Up:
What are examples of devices that operate at the Physical layer?

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11
Q

Question: A user reports that they are unable to connect to a file server. After inspecting the issue, you notice packets are being dropped between Layer 3 devices. Which layer of the OSI model should you troubleshoot next?
Answer Options:
A. Physical
B. Data Link
C. Transport
D. Network

A

Correct Answer + Explanation:
You should troubleshoot the Data Link layer, as it ensures error-free data transfer between directly connected devices. If packets are being dropped, it may be due to framing errors or MAC address issues.
Practical Use:
Issues like collisions or mismatched duplex settings can occur at this layer.
Why Others Are Incorrect:
A: Physical layer involves media and signal transmission, not framing.
C: Transport handles end-to-end communication but does not deal with direct link issues.
D: Network handles routing but assumes lower layers are functioning correctly.
Exam Objective Reference:
Domain 1.1: OSI Model - Data Link Layer.
Follow-Up:
What tools can help identify issues at the Data Link layer?

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12
Q

Question: A network administrator uses ping to test connectivity between two devices. At which OSI layer is the ping command operating?
Answer Options:
A. Application
B. Transport
C. Network
D. Data Link

A

Correct Answer + Explanation:
Ping operates at the Network layer, using the ICMP protocol to send echo requests and receive replies.
Practical Use:
ICMP is used for testing reachability and diagnosing network connectivity issues.
Why Others Are Incorrect:
A: Application layer is for user interfaces.
B: Transport layer manages reliable data delivery but doesn’t handle ICMP.
D: Data Link focuses on physical addressing and framing.
Exam Objective Reference:
Domain 1.1: OSI Model - Network Layer.
Follow-Up:
What additional tools can be used to troubleshoot at the Network layer?

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13
Q

Question: Which layer of the OSI model should be investigated when troubleshooting a corrupted file transfer over a reliable protocol?
Answer Options:
A. Application
B. Presentation
C. Transport
D. Session

A

Correct Answer + Explanation:
The Presentation layer should be investigated because it is responsible for data formatting, encryption, and compression, which can lead to corruption if not functioning correctly.
Practical Use:
Issues like mismatched encoding or decryption errors are resolved here.
Why Others Are Incorrect:
A: Application handles user interfaces and protocols like HTTP.
C: Transport ensures reliable data transfer but does not manage formatting.
D: Session handles connection management, not data corruption.
Exam Objective Reference:
Domain 1.1: OSI Model - Presentation Layer.
Follow-Up:
What protocols or tools work at the Presentation layer?

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14
Q

Question: A network technician finds that a workstation can communicate with devices on its local network but not beyond. Which OSI layer is likely at fault?
Answer Options:
A. Transport
B. Network
C. Data Link
D. Session

A

Correct Answer + Explanation:
The Network layer is likely at fault because it manages IP addressing and routing. Issues like an incorrect default gateway can restrict communication beyond the local network.
Practical Use:
Fixing routing tables or default gateway settings often resolves these issues.
Why Others Are Incorrect:
A: Transport ensures reliable communication but doesn’t handle routing.
C: Data Link handles local communication.
D: Session establishes and manages sessions but does not route traffic.
Exam Objective Reference:
Domain 1.1: OSI Model - Network Layer.
Follow-Up:
What diagnostic tools can confirm Network layer issues?

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15
Q

Question: During a VoIP call, the audio is distorted and out of sequence. Which OSI layer should be investigated to resolve the issue?
Answer Options:
A. Application
B. Presentation
C. Transport
D. Data Link

A

Correct Answer + Explanation:
The Transport layer should be investigated, as it ensures data is delivered error-free and in the correct sequence.
Practical Use:
Adjusting TCP settings or troubleshooting UDP traffic can help resolve VoIP issues.
Why Others Are Incorrect:
A: Application focuses on protocols like HTTP, not sequencing.
B: Presentation handles formatting, not timing.
D: Data Link focuses on frame delivery, not sequence.
Exam Objective Reference:
Domain 1.1: OSI Model - Transport Layer.
Follow-Up:
What protocols are typically used for VoIP at the Transport layer?

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16
Q

Question: A security administrator notices unauthorized access to a database. At which OSI layer can encryption be applied to secure the data?
Answer Options:
A. Presentation
B. Transport
C. Data Link
D. Application

A

Correct Answer + Explanation:
Encryption can be applied at the Presentation layer to secure data in transit.
Practical Use:
SSL/TLS protocols ensure data integrity and confidentiality at this layer.
Why Others Are Incorrect:
B: Transport focuses on reliable delivery but not encryption.
C: Data Link can secure frames (e.g., MACsec), but encryption at the Presentation layer secures application data.
D: Application ensures access to network services, not encryption.
Exam Objective Reference:
Domain 1.1: OSI Model - Presentation Layer.
Follow-Up:
What is an example of encryption technology used at the Presentation layer?

17
Q

Question: If multiple devices on a network experience intermittent connectivity, which OSI layer should be examined first?
Answer Options:
A. Physical
B. Data Link
C. Network
D. Session

A

Correct Answer + Explanation:
The Physical layer should be examined first, as it involves the hardware and transmission medium. Issues like damaged cables or failing network adapters often cause such problems.
Practical Use:
Using a cable tester or replacing physical hardware can resolve these issues.
Why Others Are Incorrect:
B: Data Link layer issues generally cause MAC-level problems, not physical connectivity.
C: Network issues often impact routing, not physical connectivity.
D: Session doesn’t address hardware problems.
Exam Objective Reference:
Domain 1.1: OSI Model - Physical Layer.
Follow-Up:
What tools can confirm Physical layer problems?

18
Q

Question: A user is unable to resolve domain names. Which OSI layer is involved in this issue?
Answer Options:
A. Application
B. Presentation
C. Session
D. Network

A

Correct Answer + Explanation:
The Application layer is involved because DNS operates here, enabling name resolution for network resources.
Practical Use:
Checking DNS server configurations or testing with nslookup can identify issues.
Why Others Are Incorrect:
B: Presentation deals with data formatting.
C: Session manages connections.
D: Network focuses on IP addressing and routing, not DNS.
Exam Objective Reference:
Domain 1.1: OSI Model - Application Layer.
Follow-Up:
What alternative tools can be used to troubleshoot DNS issues?

19
Q

Question: A network switch is experiencing frequent collisions. At which OSI layer is this issue occurring?
Answer Options:
A. Physical
B. Data Link
C. Transport
D. Network

A

Correct Answer + Explanation:
The Data Link layer is responsible, as collisions occur when multiple devices attempt to transmit simultaneously within the same collision domain.
Practical Use:
Implementing full-duplex communication or VLANs can help reduce collisions.
Why Others Are Incorrect:
A: Physical layer involves cables and media, not collision domains.
C: Transport handles sequencing and reliability.
D: Network addresses routing, not collisions.
Exam Objective Reference:
Domain 1.1: OSI Model - Data Link Layer.
Follow-Up:
What techniques can minimize collisions in a network?

20
Q

Question: A network administrator wants to inspect the routing table of a device. At which OSI layer does this action occur?
Answer Options:
A. Data Link
B. Network
C. Transport
D. Physical

A

Correct Answer + Explanation:
This action occurs at the Network layer, where routing tables determine the path for data packets.
Practical Use:
Commands like show ip route or netstat -r display routing tables.
Why Others Are Incorrect:
A: Data Link involves MAC addresses, not routing.
C: Transport ensures delivery, not routing.
D: Physical involves hardware, not logical tables.
Exam Objective Reference:
Domain 1.1: OSI Model - Network Layer.
Follow-Up:
What happens if the default route in a routing table is misconfigured?

21
Q

Question: A network experiencing high latency in packet delivery across multiple routers shows no issues with physical connectivity. Which OSI layer processes should be examined to identify the root cause?
Answer Options:
A. Data Link
B. Transport
C. Network
D. Session

A

Correct Answer + Explanation:
The Network layer should be examined to identify potential routing inefficiencies, such as suboptimal routes, high metric values, or misconfigured static routes.
Practical Use:
Diagnosing issues in dynamic routing protocols like OSPF or BGP often reveals latency causes.
Why Others Are Incorrect:
A: Data Link focuses on local frame delivery.
B: Transport ensures reliability and sequencing but doesn’t route packets.
D: Session handles session management, not routing.
Exam Objective Reference:
Domain 1.1: OSI Model - Network Layer.
Follow-Up:
What commands can validate routing table efficiency in this scenario?

22
Q

Question: While configuring a Layer 3 switch, you notice excessive broadcast traffic is congesting the network. Which OSI layers can be optimized to reduce broadcast storms?
Answer Options:
A. Network and Data Link
B. Data Link and Transport
C. Application and Network
D. Physical and Data Link

A

Correct Answer + Explanation:
Optimizing the Network and Data Link layers can reduce broadcast storms. VLAN segmentation at the Data Link layer and proper subnetting at the Network layer minimize unnecessary broadcast traffic.
Practical Use:
Using VLANs to isolate traffic and implementing routing policies can help control broadcasts.
Why Others Are Incorrect:
B: Transport does not manage broadcasts.
C: Application and Network layers don’t directly handle broadcast traffic.
D: Physical only deals with signal transmission.
Exam Objective Reference:
Domain 1.1: OSI Model - Data Link and Network Layers.
Follow-Up:
What additional techniques can mitigate broadcast storms?

23
Q

Question: A secure video conferencing application experiences choppy playback. Analyzing the OSI layers, which layer-specific optimizations can improve real-time streaming quality?
Answer Options:
A. Application and Presentation
B. Transport and Network
C. Data Link and Physical
D. Session and Presentation

A

Correct Answer + Explanation:
Optimizing the Transport and Network layers can improve streaming quality by prioritizing packets (QoS) and ensuring low-latency routing paths.
Practical Use:
Configuring TCP window size or enabling QoS on network devices can address latency and jitter issues.
Why Others Are Incorrect:
A: Application focuses on the software interface.
C: Physical and Data Link address lower-level connectivity.
D: Session and Presentation manage session reliability and data formatting.
Exam Objective Reference:
Domain 1.1: OSI Model - Transport and Network Layers.
Follow-Up:
What tools can measure latency and jitter at these layers?

24
Q

Question: Which OSI layer is involved when using port mirroring on a switch to analyze traffic?
Answer Options:
A. Data Link
B. Network
C. Transport
D. Physical

A

Correct Answer + Explanation:
Port mirroring operates at the Data Link layer, as it involves capturing and duplicating frames for analysis.
Practical Use:
Port mirroring is used for intrusion detection or traffic analysis using tools like Wireshark.
Why Others Are Incorrect:
B: Network handles routing, not frame duplication.
C: Transport manages end-to-end delivery but doesn’t analyze frames.
D: Physical transmits signals, not traffic capture.
Exam Objective Reference:
Domain 1.1: OSI Model - Data Link Layer.
Follow-Up:
What are the limitations of port mirroring compared to SPAN or TAP?

25
Q

Question: During troubleshooting, you observe that TCP packets are being acknowledged with excessive delay. Which OSI layer should you investigate for performance tuning?
Answer Options:
A. Network
B. Transport
C. Data Link
D. Application

A

Correct Answer + Explanation:
The Transport layer should be investigated, as it governs TCP packet acknowledgment and window sizing, which directly impact performance.
Practical Use:
Adjusting TCP window sizes or enabling selective acknowledgments (SACK) can optimize throughput.
Why Others Are Incorrect:
A: Network focuses on routing, not acknowledgments.
C: Data Link doesn’t manage TCP acknowledgments.
D: Application doesn’t handle packet flow.
Exam Objective Reference:
Domain 1.1: OSI Model - Transport Layer.
Follow-Up:
What factors influence TCP retransmissions at the Transport layer?

26
Q

Question: A network segment using fiber optic cables has frequent connection drops. Which OSI layers should be tested to identify the issue?
Answer Options:
A. Physical and Data Link
B. Data Link and Network
C. Physical and Transport
D. Session and Physical

A

Correct Answer + Explanation:
Testing the Physical and Data Link layers is critical because connection drops may be due to cable issues (Physical) or framing errors (Data Link).
Practical Use:
Using a visual fault locator for fiber and analyzing CRC errors can pinpoint the cause.
Why Others Are Incorrect:
B: Network focuses on routing, not connectivity drops.
C: Transport doesn’t deal with signal integrity.
D: Session manages connections but doesn’t test cables.
Exam Objective Reference:
Domain 1.1: OSI Model - Physical and Data Link Layers.
Follow-Up:
What tools are best suited for diagnosing fiber optic issues?

27
Q

Question: A web application uses HTTPS but fails to load for users in specific regions. Which OSI layers should be checked for the root cause?
Answer Options:
A. Application and Transport
B. Transport and Network
C. Application and Presentation
D. Data Link and Physical

A

Correct Answer + Explanation:
The Application and Presentation layers should be checked, as HTTPS involves both the application protocol and data encryption.
Practical Use:
Ensuring proper SSL/TLS configurations and verifying certificate validity can resolve such issues.
Why Others Are Incorrect:
A: Transport and Network manage data delivery, not encryption.
D: Data Link and Physical address connectivity, not application protocols.
Exam Objective Reference:
Domain 1.1: OSI Model - Application and Presentation Layers.
Follow-Up:
What diagnostic steps can verify SSL/TLS configurations?

28
Q

Question: A network engineer implements ACLs to block traffic from a specific IP range. At which OSI layer does this operation take place?
Answer Options:
A. Physical
B. Data Link
C. Network
D. Transport

A

Correct Answer + Explanation:
ACLs operate at the Network layer, filtering traffic based on IP addresses.
Practical Use:
ACLs are used in firewalls and routers to enforce security policies.
Why Others Are Incorrect:
A: Physical involves hardware and transmission.
B: Data Link focuses on MAC addresses.
D: Transport handles ports, not IP addresses.
Exam Objective Reference:
Domain 1.1: OSI Model - Network Layer.
Follow-Up:
What tools can verify ACL effectiveness?

29
Q

Question: A video stream constantly buffers despite sufficient bandwidth. Packet inspection shows high jitter. Which OSI layer is responsible for this issue?
Answer Options:
A. Transport
B. Network
C. Data Link
D. Application

A

Correct Answer + Explanation:
The Transport layer is responsible, as it handles sequencing and retransmission, which are critical to mitigating jitter.
Practical Use:
Adjusting UDP configurations or enabling QoS can help reduce jitter.
Why Others Are Incorrect:
B: Network determines routes but doesn’t control jitter.
C: Data Link focuses on frame delivery, not sequencing.
D: Application doesn’t handle packet timing.
Exam Objective Reference:
Domain 1.1: OSI Model - Transport Layer.
Follow-Up:
What metrics can identify jitter severity in a network?

30
Q

Question: During troubleshooting, a network team identifies frequent ARP table poisoning. Which OSI layer can enforce security measures to mitigate this attack?
Answer Options:
A. Data Link
B. Network
C. Application
D. Transport

A

Correct Answer + Explanation:
The Data Link layer can mitigate ARP poisoning by enabling dynamic ARP inspection (DAI) or using static ARP entries.
Practical Use:
DAI on switches can validate ARP packets and prevent spoofing.
Why Others Are Incorrect:
B: Network doesn’t handle ARP; it uses IP.
C: Application focuses on end-user services.
D: Transport doesn’t manage ARP tables.
Exam Objective Reference:
Domain 1.1: OSI Model - Data Link Layer.
Follow-Up:
What other techniques can prevent ARP poisoning?