Computer networking MCQ

1981. A walkie-talkie operates in.....

Correct Answer: Correct answer is: (B) Half duplex.

Exam Relevance: GATE, GRE, ECE exams

Difficulty: Easy

Concept notes: Half duplex communication allows for two-way communication, but not simultaneously. In a half duplex system, communication can occur in both directions, but only one direction at a time.

Common Mistakes: Students may confuse half duplex with full duplex, where communication can occur in both directions simultaneously.

Explanations: A walkie-talkie operates in half duplex mode. This means that communication can occur in both directions, but not at the same time. When one party is speaking, the other party must wait to respond. This is why users of walkie-talkies often use phrases like "over" to indicate the end of their transmission and allow the other party to respond.

Option Analysis:

Option A: Simplex communication allows for one-way communication only, which is not suitable for walkie-talkies.
Option B: Half duplex communication allows for two-way communication, but not simultaneously, which is how walkie-talkies operate.
Option C: Full duplex communication allows for simultaneous two-way communication, which is not how walkie-talkies operate.
Option D: Semi-duplex is not a standard term in communication systems and is not applicable here.

Mnemonic: Half duplex: "Half the time, you talk, the other half, you listen."

1982. Which of the following is true of many SOHO routers?

Correct Answer: Correct answer is: (C) They close down the ICMP ports by default.

Exam Relevance: CCNA, CISSP, CompTIA Network+

Difficulty: Moderate

Concept notes: ICMP (Internet Control Message Protocol) is used for error reporting and diagnostic functions. Many SOHO (Small Office/Home Office) routers are configured to block ICMP traffic by default to enhance security.

Common Mistakes: Students may mistakenly believe that DHCP, NAT, or other essential services are typically closed by default, when in fact, they are usually left open to ensure basic network functionality.

Explanations: ICMP is often blocked by default in SOHO routers to prevent potential security vulnerabilities. ICMP traffic can be used for various network diagnostics, but it can also be exploited by attackers. By closing ICMP ports, routers can reduce the risk of such attacks, thereby enhancing the security of the network.

Option Analysis:

Option A: DHCP (Dynamic Host Configuration Protocol) is typically left open to allow automatic IP address assignment to devices on the network.
Option B: NAT (Network Address Translation) is a fundamental function of routers and is not closed by default.
Option C: ICMP ports are often closed by default to enhance security.
Option D: DHCP, NAT, and ICMP are not all left open by default; ICMP is often closed.

1983. Many businesses use this Wi-Fi technology to allow the public an access point to a wireless network

Correct Answer: Correct answer is: (A) Hotspots.

Exam Relevance: IT Essentials, CompTIA A+, Network+

Difficulty: Easy

Concept notes: Wi-Fi hotspots are public access points that allow users to connect to a wireless network.

Common Mistakes: Students may confuse hotspots with other wireless technologies like Bluetooth or satellite connections.

Explanations: Hotspots are commonly used by businesses to provide public access to a wireless network. They are designed to allow multiple users to connect to the internet simultaneously, often in public places like cafes, airports, and hotels. This makes them a convenient solution for businesses to offer internet access to their customers.

Option Analysis:

Option A: Correct. Hotspots are public Wi-Fi access points used by businesses.
Option B: Incorrect. Coldspot is not a recognized term in Wi-Fi technology.
Option C: Incorrect. Satellites are used for communication over long distances, not for public Wi-Fi access.
Option D: Incorrect. Bluetooth is a short-range wireless technology used for device-to-device communication, not for public internet access.

Mnemonic: Hotspots: Hot and Spots, think of a map with hot spots for Wi-Fi.

1984. ..... substitutes eight consecutive zeros with 000VB0VB.

Correct Answer: Correct answer is: (C) B8ZS.

Exam Relevance: Digital Communications, Data Transmission, Telecommunications

Difficulty: Moderate

Concept notes: B8ZS (Bipolar with 8 zeros substitution) is a line code used in digital communications to ensure that long sequences of zeros do not cause synchronization issues.

Common Mistakes: Students often confuse B8ZS with other line coding schemes like HDB3, which also deals with zero sequences but in a different manner.

Explanations: B8ZS is specifically designed to substitute eight consecutive zeros with a pattern that includes two violations (V) and two bipolar violations (B). This ensures that the signal remains synchronized and does not lose its timing due to long sequences of zeros. The pattern 000VB0VB is used to replace eight consecutive zeros, making B8ZS the correct answer.

Option Analysis:

Option A: B4B8 is not a recognized line coding scheme for substituting zeros.
Option B: HDB3 (High-Density Bipolar 3) substitutes four consecutive zeros with a pattern that includes a violation, but not eight zeros.
Option C: B8ZS correctly substitutes eight consecutive zeros with 000VB0VB.
Option D: None of the above is incorrect as B8ZS is the correct scheme.

Mnemonic: B8ZS: "Bipolar 8 Zeros Substitution"

1985. The IEEE 802.11 standard for wireless LANs defines two services:..... and.....

Correct Answer: Correct answer is: (C) BSS; ESS.

Exam Relevance: Computer Networks, Wireless Communications, IEEE 802.11

Difficulty: Easy

Concept notes: The IEEE 802.11 standard defines two services for wireless LANs: Basic Service Set (BSS) and Extended Service Set (ESS).

Common Mistakes: Students may confuse BSS and ESS with other wireless networking terms or services.

Explanations: The IEEE 802.11 standard defines two primary services for wireless LANs: Basic Service Set (BSS) and Extended Service Set (ESS). A BSS is a set of wireless devices that can communicate with each other directly. An ESS is a collection of BSSs that are connected to form a larger network. This allows for seamless roaming between different access points within the same network.

Option Analysis:

Option A: BSS and ASS are not correct. ASS is not a defined service in the IEEE 802.11 standard.
Option B: ESS and SSS are not correct. SSS is not a defined service in the IEEE 802.11 standard.
Option C: BSS and ESS are the correct services defined by the IEEE 802.11 standard.
Option D: BSS and DCF are not correct. DCF (Distributed Coordination Function) is a medium access control method, not a service.

Mnemonic: BESS: Basic and Extended Service Set

1986. ..... are rules that govern a communication exchange.

Correct Answer: Correct answer is: (C) Protocols.

Exam Relevance: Computer Networks, Data Communication, Network Security

Difficulty: Easy

Concept notes: Protocols are predefined rules that govern the format and sequence of messages exchanged between devices in a communication network.

Common Mistakes: Students may confuse protocols with interfaces or media, which are different components of a communication system.

Explanations: Protocols define the rules for communication, including data format, timing, error checking, and other aspects necessary for successful data exchange. They ensure that devices can communicate effectively and reliably.

Option Analysis:

Option A: Media refers to the physical means of transmitting data, such as cables or wireless signals, not the rules governing communication.
Option B: Interfaces are the points of interaction between different systems or components, not the rules governing communication.
Option C: Protocols are the correct answer as they are the rules that govern the communication exchange.
Option D: All of the above is incorrect because only protocols govern the communication exchange.

1987. A computer not connected to a network is called a.....

Correct Answer: Correct answer is: (A) Stand-alone computer.

Exam Relevance: SAT, ACT, AP Computer Science Principles

Difficulty: Very Easy

Concept notes: A stand-alone computer is a computer that operates independently without being connected to a network.

Common Mistakes: Students may confuse "stand-alone" with "sit-alone," which is not a technical term.

Explanations: A stand-alone computer operates independently without being connected to a network. This term is used to describe a computer that functions on its own, without relying on other computers or network resources.

Option Analysis:

Option A: Correct. A stand-alone computer is a computer that operates independently without being connected to a network.
Option B: Incorrect. "Sit-alone" is not a technical term used in computing.
Option C: Incorrect. "Stand-in" is not a term used to describe a computer that operates independently.
Option D: Incorrect. "Sit-in" is not a term used to describe a computer that operates independently.

1988. In this type of multiplexing time slots are preassigned to sources and fixed.

Correct Answer: Correct answer is: (B) Synchronous TDM.

Exam Relevance: Computer Networks, Data Communication, Telecommunication Engineering

Difficulty: Easy

Concept notes: Synchronous TDM (Time Division Multiplexing) involves preassigning and fixing time slots for each source, ensuring a consistent and predictable transmission schedule.

Common Mistakes: Students may confuse Synchronous TDM with Asynchronous TDM, where time slots are not fixed and are allocated dynamically based on the availability of data.

Explanations: In Synchronous TDM, time slots are preassigned and fixed for each source, ensuring that each source has a dedicated time slot in every frame. This method is deterministic and allows for predictable transmission schedules, making it suitable for applications where timing is critical.

Option Analysis:

Option A: TDM is a broader term that includes both synchronous and asynchronous TDM. It does not specify the preassignment and fixing of time slots.
Option B: Synchronous TDM is the correct answer as it involves preassigning and fixing time slots for each source.
Option C: Asynchronous TDM does not preassign time slots; instead, it allocates slots dynamically based on the availability of data.
Option D: FDM (Frequency Division Multiplexing) is a different multiplexing technique that divides the bandwidth into multiple channels, not related to time slots.

1989. A vast computer network linking smaller computer networks worldwide.

Correct Answer: Correct answer is: (B) Internet.

Exam Relevance: SAT, ACT, AP Computer Science Principles

Difficulty: Easy

Concept notes: The Internet is a global network of interconnected computer networks that allows for the exchange of data and information.

Common Mistakes: Students may confuse the Internet with the World Wide Web (WWW), which is a subset of the Internet used for accessing websites and web pages.

Explanations: The Internet is a vast computer network that connects smaller networks worldwide, enabling communication and data exchange between different devices and systems. The term "Internet" specifically refers to the global network infrastructure, while the WWW is a service that operates over the Internet.

Option Analysis:

Option A: WWW (World Wide Web) is a service that operates over the Internet, not the network itself.
Option B: Internet is the correct term for the vast network connecting smaller networks worldwide.
Option C: Modem is a device that enables computers to connect to the Internet, but it is not the network itself.
Option D: TCP/IP is a set of protocols used for communication over the Internet, but it is not the network itself.

1990. To access e-mails from any machine and anywhere, we use.....

Correct Answer: Correct answer is: (C) IMAP.

Exam Relevance: CISSP, CompTIA Security+, Network+ exams

Difficulty: Moderate

Concept notes: IMAP (Internet Message Access Protocol) allows users to access emails from any device by synchronizing email messages with the server.

Common Mistakes: Students may confuse IMAP with POP (Post Office Protocol), which downloads emails to a single device and does not synchronize across multiple devices.

Explanations: IMAP is designed to keep email messages on the server, allowing users to access their emails from any device. This protocol ensures that all devices are synchronized with the latest emails, making it ideal for accessing emails from multiple machines and locations.

Option Analysis:

Option A: PGP (Pretty Good Privacy) is used for encrypting and decrypting emails, not for accessing emails from multiple devices.
Option B: PEM (Privacy Enhanced Mail) is a standard for secure email, not for accessing emails from multiple devices.
Option C: IMAP (Internet Message Access Protocol) is the correct choice as it allows users to access emails from any device by synchronizing with the server.
Option D: This option is incorrect as IMAP is the correct protocol for accessing emails from multiple devices.

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Computer networking MCQ - Set 199

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