Computer networking MCQ – Change your future

241. Formula to get length of User Data Protocol (UDP) is

Correct Answer: Correct answer is: (C) UDP length = IP length - IP header's length.

Exam Relevance: Computer Networks, CCNA, CISSP

Difficulty: Moderate

Concept notes: The correct formula for calculating the length of User Datagram Protocol (UDP) data is derived from the total IP packet length minus the length of the IP header.

Common Mistakes: Students often confuse the relationship between IP length and UDP length, leading to incorrect formulas.

Explanations: The IP packet consists of the IP header and the payload, which includes the UDP header and UDP data. The IP length field in the IP header specifies the total length of the IP packet in bytes. To find the length of the UDP data, we subtract the length of the IP header from the total IP length. This gives us the length of the UDP header and data combined. Since the UDP header is a fixed length (8 bytes), the remaining length is the UDP data.

Option Analysis:

Option A: Incorrect because adding the IP header's length to the IP length does not make sense in the context of calculating UDP data length.
Option B: Incorrect because multiplying the IP length by the IP header's length does not provide the UDP data length.
Option C: Correct because subtracting the IP header's length from the IP length gives the length of the UDP header and data combined.
Option D: Incorrect because dividing the IP length by the IP header's length does not provide the UDP data length.

242. In Three-Way Handshaking process, the situation where both the TCP's issue an active open is

Correct Answer: Correct answer is: (C) Simultaneous open.

Exam Relevance: Computer Networks, CCNA, CISSP

Difficulty: Moderate

Concept notes: In the context of TCP (Transmission Control Protocol), a simultaneous open occurs when both endpoints initiate a connection request at the same time.

Common Mistakes: Students may confuse simultaneous open with mutual open, which is not a standard term in TCP handshaking.

Explanations: In a simultaneous open, both TCP endpoints send a SYN (synchronize) packet to each other at the same time. This situation is rare but possible and is handled by the TCP protocol to ensure that both endpoints can establish a connection without conflict. The term "simultaneous open" accurately describes this scenario where both sides initiate the connection process concurrently.

Option Analysis:

Option A: Mutual open is not a standard term in TCP handshaking and does not describe the situation where both endpoints initiate a connection simultaneously.
Option B: Mutual Close refers to the process where both endpoints agree to terminate the connection, which is unrelated to the initial connection establishment.
Option C: Simultaneous open correctly describes the situation where both TCP endpoints initiate a connection request at the same time.
Option D: Simultaneous close is the process where both endpoints terminate the connection at the same time, which is unrelated to the initial connection establishment.

243. How many types of frames does IEEE 802.11 LANs use?

Correct Answer: Correct answer is: (D) None of the above.

Exam Relevance: Computer Networks, CCNA, CISSP

Difficulty: Moderate

Concept notes: IEEE 802.11 LANs use more than 5 types of frames, including data frames, management frames, and control frames, each with subtypes.

Common Mistakes: Students may incorrectly assume that IEEE 802.11 LANs use only a limited number of frame types, such as data and management frames, without considering the subtypes and control frames.

Explanations: IEEE 802.11 LANs use a variety of frame types to support different functions within the network. These include data frames for transmitting user data, management frames for managing connections and network access, and control frames for managing the medium access control. Each of these categories has multiple subtypes, such as association request, association response, beacon, probe request, probe response, RTS (Request to Send), CTS (Clear to Send), and more. Therefore, the number of frame types exceeds 5, making the correct answer "None of the above."

Option Analysis:

Option A: Incorrect, as IEEE 802.11 uses more than 6 frame types.
Option B: Incorrect, as IEEE 802.11 uses more than 4 frame types.
Option C: Incorrect, as IEEE 802.11 uses more than 5 frame types.
Option D: Correct, as IEEE 802.11 uses more than 5 frame types, making the other options incorrect.

244. Which of the following is not true about User Datagram Protocol in transport layer?

Correct Answer: Correct answer is: (B) It does three way handshake before sending datagrams.

Exam Relevance: Computer Networks, CCNA, CISSP

Difficulty: Moderate

Concept notes: User Datagram Protocol (UDP) is a connectionless protocol that does not perform a three-way handshake before sending datagrams.

Common Mistakes: Students often confuse UDP with TCP, which does perform a three-way handshake.

Explanations: UDP is a connectionless protocol, meaning it does not establish a connection before sending data. Unlike TCP, which requires a three-way handshake to establish a connection, UDP sends data immediately without any prior connection setup. This makes UDP suitable for applications that require low latency and do not need the reliability features provided by TCP.

Option Analysis:

Option A: UDP is indeed suitable for unidirectional communication and broadcasting, as it does not require a connection setup.
Option B: UDP does not perform a three-way handshake before sending datagrams, making this statement incorrect.
Option C: UDP provides datagrams, which are suitable for modeling other protocols such as IP tunneling, Remote Procedure Call (RPC), and the Network File System (NFS).
Option D: The lack of retransmission delays in UDP makes it suitable for real-time applications such as streaming video or audio.

245. If a router sends every incoming packet out only on those lines that are going approximately in the right direction is known as.....

Correct Answer: Correct answer is: (C) Selective flooding.

Exam Relevance: CCNA, Network+, CompTIA Network+

Difficulty: Moderate

Concept notes: Selective flooding is a routing technique where a router forwards packets only on the interfaces that are in the general direction of the destination.

Common Mistakes: Students may confuse selective flooding with random flooding, where packets are sent out on all interfaces.

Explanations: Selective flooding is a method used in routing where a router forwards packets only on the interfaces that are in the general direction of the destination. This approach reduces unnecessary traffic and improves network efficiency by avoiding the flooding of packets on all interfaces.

Option Analysis:

Option A: Random flooding involves sending packets out on all interfaces, which is not the case here.
Option B: Static flooding is not a standard term in routing and does not describe the behavior of sending packets in the right direction.
Option C: Selective flooding is the correct term for sending packets only on the interfaces that are in the general direction of the destination.
Option D: Early flooding is not a standard term and does not describe the behavior of sending packets in the right direction.

246. Data from a computer are.....; the local loop handles..... signals.

Correct Answer: Correct answer is: (D) Digital; analog.

Exam Relevance: Networking exams, Telecommunications exams, Computer Science exams

Difficulty: Moderate

Concept notes: Data from a computer is typically digital, while the local loop, which connects the computer to the telephone network, handles analog signals.

Common Mistakes: Students may confuse the nature of signals in the local loop, thinking it also handles digital signals.

Explanations: Data from a computer is digital because computers process and store information in binary form (0s and 1s). The local loop, however, is part of the telephone network infrastructure, which traditionally uses analog signals to transmit voice and data over copper wires. Therefore, the local loop must convert digital signals from the computer into analog signals for transmission over the telephone network.

Option Analysis:

Option A: Incorrect because data from a computer is digital, not analog.
Option B: Incorrect because the local loop handles analog signals, not digital.
Option C: Incorrect because the local loop does not handle digital signals.
Option D: Correct because data from a computer is digital and the local loop handles analog signals.

Mnemonic: Digital Data, Analog Loop

247. What is the size of Host bits in Class B of IP address?

Correct Answer: Correct answer is: (C) 16.

Exam Relevance: CCNA, CISSP, CompTIA Network+

Difficulty: Moderate

Concept notes: In IP addressing, Class B addresses have a 16-bit host portion.

Common Mistakes: Students may confuse the host bits with the network bits or the total number of bits in an IP address.

Explanations: Class B IP addresses use the first 16 bits for the network portion and the last 16 bits for the host portion. Therefore, the size of the host bits in a Class B IP address is 16 bits.

Option Analysis:

Option A: 4 bits is incorrect as it is too small for the host portion in a Class B address.
Option B: 8 bits is incorrect as it is also too small for the host portion in a Class B address.
Option C: 16 bits is correct as it matches the size of the host portion in a Class B address.
Option D: 32 bits is incorrect as it would encompass the entire IP address, not just the host portion.

248. What is the port number of the FTP?

Correct Answer: Correct answer is: (C) 20/21.

Exam Relevance: CCNA, CISSP, CompTIA Network+

Difficulty: Easy

Concept notes: FTP (File Transfer Protocol) uses two port numbers: 20 for data transfer and 21 for control commands.

Common Mistakes: Students often confuse FTP port numbers with other protocols, such as SMTP (25) or Telnet (23).

Explanations: FTP uses two ports: port 21 for control commands and port 20 for data transfer. Port 21 is used to establish a connection and send commands, while port 20 is used to transfer files. Therefore, the correct answer is 20/21.

Option Analysis:

Option A: Port 25 is used for SMTP (Simple Mail Transfer Protocol), not FTP.
Option B: Port 23 is used for Telnet, not FTP.
Option C: FTP uses ports 20 and 21 for data transfer and control commands, respectively.
Option D: Port 27960 is used for games like Quake III Arena, not FTP.

Mnemonic: FTP: 20/21, Data/Control

249. In a bridged LAN, the..... algorithm creates a topology in which each LAN can be reached from any other LAN through one path only.

Correct Answer: Correct answer is: (A) Spanning tree.

Exam Relevance: CCNA, Network+, CompTIA Network+

Difficulty: Moderate

Concept notes: The spanning tree algorithm is used in bridged LANs to create a loop-free topology, ensuring that each LAN can be reached from any other LAN through a single path.

Common Mistakes: Students may confuse the spanning tree algorithm with other tree structures like binary or unary trees, which are not used for network topology.

Explanations: The spanning tree algorithm is specifically designed to prevent loops in a network by creating a tree-like structure where each node (or LAN) is connected to the network through a single path. This ensures that there are no redundant paths, which can cause issues like broadcast storms and infinite loops. The algorithm is crucial in maintaining network efficiency and reliability in bridged LAN environments.

Option Analysis:

Option A: Correct. The spanning tree algorithm is used to create a loop-free topology in bridged LANs.
Option B: Incorrect. Binary trees are not used for network topology in bridged LANs.
Option C: Incorrect. Unary trees are not used for network topology in bridged LANs.
Option D: Incorrect. The correct answer is provided in option A.

250. The maximum speed is 100 Mbps.

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

Exam Relevance: AP Computer Science Principles, SAT Subject Test in Computer Science

Difficulty: Moderate

Concept notes: DSL (Digital Subscriber Line) technology provides internet access over telephone lines and can support speeds up to 100 Mbps, depending on the specific DSL technology and the distance from the user to the service provider's equipment.

Common Mistakes: Students may confuse DSL with other internet connection types, such as dial-up or satellite, which typically offer lower speeds.

Explanations: DSL technology can achieve speeds up to 100 Mbps, making it a suitable choice for high-speed internet access. This speed is significantly higher than dial-up and satellite connections, which are generally slower. Fiber-optic connections can also provide high speeds, but the question specifies a maximum speed of 100 Mbps, which aligns with DSL capabilities.

Option Analysis:

Option A: Dial-up connections are much slower, typically up to 56 Kbps, which is far below the 100 Mbps mentioned in the question.
Option B: DSL can support speeds up to 100 Mbps, making it the correct answer.
Option C: Fiber-optic connections can provide speeds much higher than 100 Mbps, but the question specifies a maximum speed of 100 Mbps, which is more aligned with DSL.
Option D: Satellite connections are generally slower and less reliable than DSL, with speeds typically ranging from 12 Mbps to 25 Mbps.

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Computer networking MCQ - Set 25

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