AP Computer Science Principles Quiz: Fault Tolerance

What this quiz covers

This quiz focuses on Fault Tolerance, giving you a quick way to practice the rules, question types, and explanations that matter most for AP Computer Science Principles.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. A fault-tolerant system would use a single, more reliable switch instead of two.
2. In a fault-tolerant system, the backup switch would be automatically and instantly activated upon failure, without manual intervention. (correct answer)
3. A fault-tolerant system would not require switches and would connect all computers directly to each other.
4. In a fault-tolerant system, the backup switch would be from a different manufacturer to avoid common bugs.

Explanation: Having a spare part is a form of redundancy, but fault tolerance implies the system can handle the failure automatically with minimal or no downtime. This setup, known as a cold spare, requires manual intervention and results in system downtime, whereas a hot spare in a truly fault-tolerant system would take over automatically.

Question 2

1. Upgrade the existing Internet connection to a higher bandwidth plan.
2. Purchase a second, separate Internet connection from a different service provider. (correct answer)
3. Install a new, more powerful router to replace the one provided by the current provider.
4. Set up a local server to cache frequently visited websites to reduce Internet usage.

Explanation: This action introduces redundancy for the entire Internet connection. If the primary provider has an outage, the business can switch to the secondary provider, thus continuing operations. This directly addresses the single point of failure.

Question 3

1. High-speed data transfer
2. Fault tolerance (correct answer)
3. Data encryption
4. Open protocols

Explanation: The need for a network that could survive the loss of some of its nodes is the very definition of fault tolerance. This foundational requirement shaped the Internet's decentralized, packet-switched architecture with redundant paths.

Question 4

1. A decrease in the overall speed of the system because of the complexity of managing duplicate components.
2. An increase in costs and complexity due to the need for additional hardware, software, and maintenance. (correct answer)
3. A reduction in system security, as redundant components can provide more points of entry for attackers.
4. A limit on the system's ability to scale, since redundancy works best for small, contained networks.

Explanation: Implementing redundancy involves duplicating components (like servers, network paths, power supplies), which adds to the initial cost and the ongoing complexity of managing the system. This is a key trade-off against the benefit of increased reliability.

Question 5

1. The platform has a fault-tolerant design with multiple redundant servers, and traffic was automatically rerouted to working servers. (correct answer)
2. The users' web browsers had cached all the images, so they did not need to connect to the server.
3. The platform's protocol automatically fixed the software bug on the crashed server and restarted it instantly.
4. The platform uses a lossless compression algorithm, which reduces the load on the servers and prevents them from crashing.

Explanation: This scenario describes a classic case of fault tolerance in action. The failure of a single component (one server) did not cause a failure of the entire system because redundant components (other servers) were available to take over its workload.

Question 6

1. It establishes a dedicated, fixed circuit between two communicating devices, guaranteeing the connection quality.
2. It ensures all packets in a message arrive in the correct sequence by numbering them before transmission.
3. It allows each data packet to be routed independently, enabling the network to bypass failed or congested links. (correct answer)
4. It bundles data from multiple users into a single packet to maximize the use of the network's bandwidth.

Explanation: The independent routing of packets is key. Unlike circuit switching, which uses a fixed path, packet switching allows the network to be flexible and adaptive. If one path fails, only the packets currently on that path are lost; subsequent packets can be sent on working routes.

Question 7

1. A user protects their account with a password and a fingerprint scan.
2. A file is compressed to a smaller size before being sent over a network.
3. An airline's booking system runs on identical servers in two geographically separate locations. (correct answer)
4. A program is broken into smaller tasks that can be run simultaneously on multiple processors.

Explanation: This is a clear example of redundancy for fault tolerance. The identical servers are duplicate components. If one location fails, the other can take over, ensuring the booking system remains available.

Question 8

1. It encrypted data to hide sensor names
2. It detected errors and requested resend (correct answer)
3. It boosted volume so alerts sounded louder
4. It deleted packets to prevent delays

Explanation: This question tests AP Computer Science Principles skills, specifically understanding fault tolerance in computing systems and networks. Fault tolerance is the ability of a system to continue operating properly in the event of a failure of some of its components. It involves mechanisms like redundancy, error detection and correction, and failover. In the passage, the system uses error detection and correction by adding check values to packets and requesting retransmission when errors are detected. Choice B is correct because it accurately describes how the system detects errors through check values and requests resending of corrupted packets. Choice A is incorrect because encryption is about security and privacy, not error detection - the passage specifically mentions detecting bit flips from interference. To help students, emphasize the difference between error detection (finding mistakes) and other fault tolerance mechanisms. Practice identifying checksum/parity concepts and how they enable reliable communication over unreliable channels.

Question 9

1. It split traffic evenly to speed uploads
2. It switched service to a backup server (correct answer)
3. It permanently shut down the service
4. It reduced file sizes before sending

Explanation: This question tests AP Computer Science Principles skills, specifically understanding fault tolerance in computing systems and networks. Fault tolerance is the ability of a system to continue operating properly in the event of a failure of some of its components. It involves mechanisms like redundancy, error detection and correction, and failover. In the passage, the system uses automatic failover to maintain functionality when the primary server crashes, switching users to a backup server within seconds. Choice B is correct because it accurately reflects how the system automatically switched service to the backup server when the primary failed, which is the definition of failover. Choice A is incorrect because it describes load balancing, not failover - the system didn't split traffic evenly but rather redirected all traffic to the backup. To help students, emphasize that failover specifically involves switching from a failed component to a working backup, not distributing load. Practice identifying the difference between failover (switching to backup) and load balancing (distributing work).

Question 10

1. It reduces the price of electricity
2. It keeps services available during outages (correct answer)
3. It speeds up website loading every day
4. It prevents any component from failing

Explanation: This question tests AP Computer Science Principles skills, specifically understanding fault tolerance in computing systems and networks. Fault tolerance is the ability of a system to continue operating properly in the event of a failure of some of its components. It involves mechanisms like redundancy, error detection and correction, and failover. In the passage, the system uses multiple layers of redundancy including two power feeds, battery units, and diesel generators to maintain continuous power supply. Choice B is correct because it accurately identifies that redundancy keeps services available during outages, as demonstrated when the hospital websites remained accessible throughout the storm. Choice D is incorrect because redundancy doesn't prevent failures but rather ensures continued operation despite failures. To help students, emphasize that redundancy provides backup options rather than preventing failures entirely. Watch for: confusion between prevention and mitigation strategies, and overgeneralization about what redundancy can achieve.

Question 11

1. Automatic Failover to another region (correct answer)
2. Manual typing of each customer request
3. Extra animations to keep users engaged
4. A larger logo to improve brand recall

Explanation: This question tests AP Computer Science Principles skills, specifically understanding fault tolerance in computing systems and networks. Fault tolerance is the ability of a system to continue operating properly in the event of a failure of some of its components. It involves mechanisms like redundancy, error detection and correction, and failover. In the passage, the cloud service uses automatic failover between regions - when Region 1 has an outage, the provider automatically redirects requests to Region 2. Choice A is correct because it accurately identifies automatic failover as the mechanism that maintains service by switching from the failed region to a working region. Choice B is incorrect because manual typing of requests would be inefficient and doesn't relate to automated fault tolerance mechanisms. To help students, emphasize that cloud providers often use geographic redundancy with automatic failover between regions. Practice identifying how DNS redirection and load balancers enable seamless regional failover.

Question 12

1. It switched checkout to the standby server (correct answer)
2. It compressed images to load pages faster
3. It prevented any server from ever failing
4. It caused checkout to stop until repairs

Explanation: This question tests AP Computer Science Principles skills, specifically understanding fault tolerance in computing systems and networks. Fault tolerance is the ability of a system to continue operating properly in the event of a failure of some of its components. It involves mechanisms like redundancy, error detection and correction, and failover. In the passage, the system uses failover when the active server's disk fails - the standby server takes over the same network address and continues processing. Choice A is correct because it accurately describes the failover process where checkout switched from the failed active server to the standby server. Choice C is incorrect because failover doesn't prevent failures from occurring; it provides a mechanism to continue operating when failures do happen. To help students, emphasize that failover involves automatic switching to backup systems when primary systems fail. Practice identifying active-standby configurations and how they maintain service continuity.

Question 13

1. Error detection and correction in messages (correct answer)
2. Load balancing across multiple web pages
3. Adding more drivers to reduce traffic
4. Turning off updates to avoid wrong data

Explanation: This question tests AP Computer Science Principles skills, specifically understanding fault tolerance in computing systems and networks. Fault tolerance is the ability of a system to continue operating properly in the event of a failure of some of its components. It involves mechanisms like redundancy, error detection and correction, and failover. In the passage, the system uses error detection and correction through extra bits that help spot errors and rebuild original data when messages are corrupted by weak signals. Choice A is correct because it accurately identifies error detection and correction as the mechanism that ensures reliable communication despite transmission errors. Choice B is incorrect because load balancing distributes work across resources, which is different from correcting transmission errors in messages. To help students, emphasize that error correction codes allow systems to recover from data corruption without retransmission. Practice identifying different error handling strategies: detection only vs. detection and correction.

Question 14

1. A system designed to prevent any and all component failures from occurring through rigorous testing.
2. A system that can continue to function, potentially at a reduced level, even when one or more of its components fail. (correct answer)
3. A system optimized to perform computations at the highest possible speed, minimizing processing time.
4. A system that uses advanced encryption to protect itself from all types of unauthorized access and cyberattacks.

Explanation: Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of some of its components. It does not prevent failures but allows the system to cope with them.

Question 15

1. The use of high-bandwidth fiber-optic cables for all major data pathways.
2. The hierarchical structure of domain names (DNS) for locating servers.
3. The implementation of redundancy through multiple, alternative data routing paths. (correct answer)
4. The requirement for all connected devices to have a unique IP address.

Explanation: The Internet's fault tolerance is largely achieved through redundancy. Data packets can be rerouted through many different paths, so the failure of a single path does not typically stop data from reaching its destination.

Question 16

1. Installing more powerful servers within the existing single data center to handle traffic more efficiently.
2. Increasing the bandwidth of the Internet connection to the single data center to allow for faster data transfer.
3. Creating a complete, mirrored copy of the website and its database in a separate data center in a different geographic location. (correct answer)
4. Implementing a more complex password policy for customer accounts to improve overall system security.

Explanation: This strategy introduces redundancy at a large scale. If one data center fails (due to a power outage or other issue), the system can redirect traffic to the mirrored site in the other location, allowing the service to continue functioning.

Question 17

1. If one of the connected devices fails, it may disrupt traffic for all other devices on the network.
2. The central switch represents a single point of failure; if it malfunctions, the entire network will cease to function. (correct answer)
3. The network's performance will decrease significantly as more devices are added and communicate simultaneously.
4. Data packets can collide if two devices attempt to send data at the exact same time through the switch.

Explanation: In a star topology, the central switch is a critical component. Its failure will disconnect all devices from each other, making it a single point of failure and a major vulnerability for fault tolerance.

Question 18

1. It guarantees that data packets always travel along the shortest possible path to minimize latency.
2. It allows routers to automatically find alternative paths for data when a preferred path becomes unavailable. (correct answer)
3. It encrypts packet data during transmission, preventing unauthorized users from reading the information.
4. It breaks large files into smaller packets, which are easier for the network to handle and process.

Explanation: Dynamic routing protocols enable routers to communicate with each other and update their routing tables based on network conditions. If a link or router fails, the protocols can detect this change and reroute traffic through working paths, which is a key aspect of the Internet's fault tolerance.

Question 19

1. A failure of the main database server's hard drive, which would cause temporary data inaccessibility.
2. A localized event like a fire or building-wide power outage that affects both servers simultaneously. (correct answer)
3. A software bug that corrupts a single patient record on the main server before the hourly backup.
4. A slow network connection between the main server and the backup server, delaying the copy process.

Explanation: Keeping the backup server in the same building means that a single, localized disaster could destroy both the primary and backup systems. This identifies a vulnerability where the redundancy is insufficient to protect against a large-scale failure affecting the entire location.

Question 20

1. It ensures that the cost of accessing the Internet remains low for all users.
2. It allows for the rapid development of new communication protocols.
3. It increases the overall reliability of the network, allowing communication to continue despite component failures. (correct answer)
4. It enables data to be transmitted at the maximum possible speed allowed by the physical infrastructure.

Explanation: The primary benefit of fault tolerance is reliability. By being able to withstand failures of individual parts, the overall system remains available and functional for its users, which is crucial for a global communication network like the Internet.